/* ============================================
   SplitXpense - Premium fintech design system
   A calm, trustworthy expense splitting experience
   ============================================ */

/* ============================================
   1. DESIGN TOKENS & CSS VARIABLES
   ============================================ */
/* Font loaded via <link> in HTML to avoid duplicate request */

:root {
    /* === COLOR PALETTE === */
    
    /* Primary - Vibrant Green (Trustworthy & Rewarding) */
    --primary-50: #f0fdf4;
    --primary-100: #dcfce7;
    --primary-200: #bbf7d0;
    --primary-300: #86efac;
    --primary-400: #4ade80;
    --primary-500: #22c55e;
    --primary-600: #16a34a;
    --primary-700: #15803d;
    --primary-800: #166534;
    --primary-900: #14532d;
    
    /* Accent - Soft Indigo */
    --accent-50: #eef2ff;
    --accent-100: #e0e7ff;
    --accent-200: #c7d2fe;
    --accent-300: #a5b4fc;
    --accent-400: #818cf8;
    --accent-500: #6366f1;
    --accent-600: #4f46e5;
    --accent-700: #4338ca;
    --accent-800: #3730a3;
    --accent-900: #312e81;
    
    /* Success - Positive Balance (Teal Green) */
    --success-50: #f0fdf4;
    --success-100: #dcfce7;
    --success-200: #bbf7d0;
    --success-300: #86efac;
    --success-400: #4ade80;
    --success-500: #22c55e;
    --success-600: #16a34a;
    --success-700: #15803d;
    --success-800: #166534;
    --success-900: #14532d;
    
    /* Warning - Soft Amber */
    --warning-50: #fffbeb;
    --warning-100: #fef3c7;
    --warning-200: #fde68a;
    --warning-300: #fcd34d;
    --warning-400: #fbbf24;
    --warning-500: #f59e0b;
    --warning-600: #d97706;
    --warning-700: #b45309;
    --warning-800: #92400e;
    --warning-900: #78350f;
    
    /* Danger - Dark Red (Bold & Serious) */
    --danger-50: #fef2f2;
    --danger-100: #fee2e2;
    --danger-200: #fecaca;
    --danger-300: #fca5a5;
    --danger-400: #ef4444;
    --danger-500: #b91c1c;
    --danger-600: #991b1b;
    --danger-700: #7f1d1d;
    --danger-800: #6b1515;
    --danger-900: #501010;
    
    /* Neutrals - Warm Gray */
    --gray-50: #fafafa;
    --gray-100: #f4f4f5;
    --gray-200: #e4e4e7;
    --gray-300: #d4d4d8;
    --gray-400: #a1a1aa;
    --gray-500: #71717a;
    --gray-600: #52525b;
    --gray-700: #3f3f46;
    --gray-800: #27272a;
    --gray-900: #18181b;
    
    /* Semantic Colors */
    --color-positive: var(--primary-600);
    --color-positive-bg: var(--primary-50);
    --color-negative: #e53e3e;
    --color-negative-bg: var(--danger-50);
    --color-settled: var(--gray-400);
    
    /* === THEME COLORS === */
    --background: #f8fafc;
    --background-subtle: #f1f5f9;
    --surface: #ffffff;
    --surface-elevated: #ffffff;
    --border: #e2e8f0;
    --border-subtle: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --text-tertiary: #94a3b8;
    --text-inverse: #ffffff;
    
    /* === SHADOWS === */
    --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.03);
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.04), 0 1px 2px -1px rgba(0, 0, 0, 0.03);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.06), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.07), 0 8px 10px -6px rgba(0, 0, 0, 0.04);
    --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
    --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.04);
    
    /* Colored shadows for depth */
    --shadow-primary: 0 4px 14px -3px rgba(16, 185, 129, 0.25);
    --shadow-accent: 0 4px 14px -3px rgba(99, 102, 241, 0.25);
    --shadow-danger: 0 4px 14px -3px rgba(244, 63, 94, 0.2);
    
    /* === SPACING === */
    --space-0: 0;
    --space-1: 0.25rem;  /* 4px */
    --space-2: 0.5rem;   /* 8px */
    --space-3: 0.75rem;  /* 12px */
    --space-4: 1rem;     /* 16px */
    --space-5: 1.25rem;  /* 20px */
    --space-6: 1.5rem;   /* 24px */
    --space-8: 2rem;     /* 32px */
    --space-10: 2.5rem;  /* 40px */
    --space-12: 3rem;    /* 48px */
    --space-16: 4rem;    /* 64px */
    --space-20: 5rem;    /* 80px */
    --header-height: 4rem; /* fixed header height for top padding (ensure content clears header) */
    
    /* === TYPOGRAPHY === */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'SF Mono', Consolas, monospace;
    
    --text-xs: 0.75rem;     /* 12px */
    --text-sm: 0.875rem;    /* 14px */
    --text-base: 1rem;      /* 16px */
    --text-lg: 1.125rem;    /* 18px */
    --text-xl: 1.25rem;     /* 20px */
    --text-2xl: 1.5rem;     /* 24px */
    --text-3xl: 1.875rem;   /* 30px */
    --text-4xl: 2.25rem;    /* 36px */
    --text-5xl: 3rem;       /* 48px */
    
    --font-light: 300;
    --font-normal: 400;
    --font-medium: 500;
    --font-semibold: 600;
    --font-bold: 700;
    --font-extrabold: 800;
    
    --leading-tight: 1.25;
    --leading-snug: 1.375;
    --leading-normal: 1.5;
    --leading-relaxed: 1.625;
    
    --tracking-tight: -0.025em;
    --tracking-normal: 0;
    --tracking-wide: 0.025em;
    
    /* === BORDERS === */
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-2xl: 20px;
    --radius-3xl: 24px;
    --radius-full: 9999px;
    
    /* === TRANSITIONS === */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 200ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 300ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-bounce: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* === Z-INDEX === */
    --z-dropdown: 100;
    --z-sticky: 200;
    --z-modal-backdrop: 900;
    --z-modal: 1000;
    --z-notification: 1100;
}

/* ============================================
   2. BASE RESET & GLOBAL STYLES
   ============================================ */

*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
    -webkit-tap-highlight-color: transparent;
}

html {
    width: 100%;
    overflow-x: hidden;
}
body {
    font-family: var(--font-family);
    background-color: var(--background);
    color: var(--text-primary);
    line-height: var(--leading-normal);
    font-size: var(--text-base);
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    min-height: 100vh;
    width: 100%;
    max-width: 100vw;
    margin: 0;
    overflow-x: hidden;
}

/* Selection styling */
::selection {
    background: var(--primary-200);
    color: var(--primary-900);
}

/* Smooth scroll for anchor links */
@media (prefers-reduced-motion: no-preference) {
    html {
        scroll-behavior: smooth;
    }
}

/* ============================================
   3. TYPOGRAPHY
   ============================================ */

h1, h2, h3, h4, h5, h6 {
    font-weight: var(--font-bold);
    line-height: var(--leading-tight);
    letter-spacing: var(--tracking-tight);
    color: var(--text-primary);
}

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }
h5 { font-size: var(--text-base); font-weight: var(--font-semibold); }
h6 { font-size: var(--text-sm); font-weight: var(--font-semibold); }

p {
    color: var(--text-secondary);
    line-height: var(--leading-relaxed);
}

a {
    color: var(--primary-600);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--primary-700);
}

/* ============================================
   4. LAYOUT & CONTAINERS
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-4);
}

@media (min-width: 640px) {
    .container {
        padding: 0 var(--space-6);
    }
}

@media (min-width: 1024px) {
    .container {
        padding: 0 var(--space-8);
    }
}

/* ============================================
   5. HEADER
   ============================================ */

header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    width: 100%;
    z-index: var(--z-sticky);
    background: var(--surface);
    padding: var(--space-4) 0;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
    border-bottom: 1px solid var(--border-subtle);
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--space-4);
}

.logo {
    flex-shrink: 0;
}

.logo h1 {
    font-size: var(--text-xl);
    font-weight: var(--font-extrabold);
    background: linear-gradient(135deg, var(--primary-600) 0%, var(--primary-500) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.03em;
    margin: 0;
    line-height: 1.2;
}

.logo p {
    color: var(--text-tertiary);
    font-size: var(--text-xs);
    margin: var(--space-1) 0 0 0;
    font-weight: var(--font-medium);
    letter-spacing: var(--tracking-wide);
}

/* App wrapper: full width on all screens, flex only for footer placement */
.app-wrapper {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    width: 100%;
    max-width: 100%;
}
.app-wrapper > main {
    flex: 1 1 auto;
    width: 100%;
    padding-top: var(--header-height);
}

/* App footer – minimal, on-brand, blends with page */
.app-footer {
    flex-shrink: 0;
    margin-top: auto;
    padding: var(--space-1) var(--space-1) var(--space-5);
    background: transparent;
    width: 100%;
}
.app-footer-inner {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-1);
    text-align: center;
    max-width: 480px;
    margin: 0 auto;
}
.app-footer-brand {
    display: inline-flex;
    align-items: center;
    gap: var(--space-1);
    text-decoration: none;
    color: var(--text-primary);
    transition: opacity var(--transition-fast);
}
.app-footer-brand:hover {
    opacity: 0.85;
}
.app-footer-brand img {
    height: 28px;
    width: auto;
    display: block;
}
.app-footer-name {
    font-size: var(--text-sm);
    font-weight: var(--font-semibold);
    letter-spacing: -0.02em;
}
.app-footer-tagline {
    margin: 0;
    font-size: var(--text-xs);
    color: var(--text-tertiary);
    font-weight: var(--font-medium);
    letter-spacing: 0.02em;
}
.app-footer-meta {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--space-2);
    font-size: var(--text-xs);
    color: var(--text-tertiary);
}
.app-footer-link {
    color: var(--primary-600);
    text-decoration: none;
    font-weight: var(--font-medium);
}
.app-footer-link:hover {
    color: var(--primary-700);
    text-decoration: underline;
}
.app-footer-dot {
    color: var(--text-tertiary);
    opacity: 0.6;
    user-select: none;
}
.app-footer-copy {
    color: var(--text-tertiary);
}

.user-info {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    flex-wrap: wrap;
    justify-content: flex-end;
}

#currentUserName {
    color: var(--text-primary);
    font-weight: var(--font-semibold);
    font-size: var(--text-sm);
}

.user-info .btn-link {
    color: var(--primary-600);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    background: transparent;
    border: none;
    cursor: pointer;
}

/* Edit user name button - flip pencil icon to point left */
.user-info .btn-link[data-action="showEditUserNameModal"] {
    transform: scaleX(-1);
}

.user-info .btn-link:hover {
    background: var(--primary-50);
    color: var(--primary-700);
}

/* Group Detail Header */
.group-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    width: 100%;
    z-index: var(--z-sticky);
    background: var(--surface);
    border-bottom: 1px solid var(--border-subtle);
    padding: var(--space-4) 0;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.group-header + main {
    padding-top: var(--header-height);
}

/* First block in group detail (Total Expenses) stays visible below fixed header */
.group-header + main .total-expenses {
    scroll-margin-top: var(--header-height);
}

.group-header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--space-4);
}

.group-header-left {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    flex: 1;
    min-width: 0;
}

.btn-back {
    background: transparent;
    border: none;
    font-size: var(--text-xl);
    cursor: pointer;
    color: var(--text-secondary);
    padding: 0;
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.btn-back:hover {
    color: var(--primary-600);
}

.group-info {
    flex: 1;
    min-width: 0;
}

.group-info h1 {
    margin: 0 0 var(--space-1) 0;
    font-size: var(--text-xl);
    color: var(--text-primary);
    word-break: break-word;
    line-height: var(--leading-tight);
    font-weight: var(--font-bold);
}

.group-info p {
    color: var(--text-tertiary);
    font-size: var(--text-sm);
    margin: 0;
    line-height: var(--leading-normal);
    font-weight: var(--font-normal);
}

.group-actions {
    display: flex;
    gap: var(--space-2);
    flex-shrink: 0;
}

/* ============================================
   6. BUTTONS
   ============================================ */

/* Base Button */
.btn-primary, .btn-success, .btn-secondary, .btn-danger, .btn-link, .btn-add {
    border: none;
    padding: var(--space-3) var(--space-5);
    border-radius: var(--radius-lg);
    cursor: pointer;
    font-weight: var(--font-semibold);
    font-size: var(--text-sm);
    font-family: inherit;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    min-height: 44px;
    letter-spacing: var(--tracking-normal);
    text-decoration: none;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

/* Primary/Success Button - Main CTA */
.btn-success, .btn-primary {
    background: linear-gradient(135deg, var(--primary-500) 0%, var(--primary-600) 100%);
    color: var(--text-inverse);
    box-shadow: var(--shadow-sm), var(--shadow-primary);
}

.btn-success:hover, .btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-600) 0%, var(--primary-700) 100%);
    box-shadow: var(--shadow-md), var(--shadow-primary);
    transform: translateY(-1px);
}

.btn-success:active, .btn-primary:active {
    transform: translateY(0);
    box-shadow: var(--shadow-xs);
}

/* Secondary Button */
.btn-secondary {
    background: var(--gray-100);
    color: var(--text-secondary);
    box-shadow: var(--shadow-xs);
}

.btn-secondary:hover {
    background: var(--gray-200);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.btn-secondary:active {
    transform: translateY(0);
}

/* Danger Button - Soft Coral */
.btn-danger {
    background: linear-gradient(135deg, var(--danger-400) 0%, var(--danger-500) 100%);
    color: var(--text-inverse);
    box-shadow: var(--shadow-sm), var(--shadow-danger);
}

.btn-danger:hover {
    background: linear-gradient(135deg, var(--danger-500) 0%, var(--danger-600) 100%);
    box-shadow: var(--shadow-md), var(--shadow-danger);
    transform: translateY(-1px);
}

.btn-danger:active {
    transform: translateY(0);
}

/* Link Button */
.btn-link {
    background: none;
    border: none;
    color: var(--primary-600);
    padding: var(--space-2) var(--space-3);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
}

.btn-link:hover {
    color: var(--primary-700);
    background: var(--primary-50);
}

/* Add Button */
.btn-add {
    background: var(--surface);
    border: 2px dashed var(--border);
    color: var(--text-tertiary);
    font-size: var(--text-xl);
    font-weight: var(--font-light);
    width: 44px;
    height: 44px;
    padding: 0;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.btn-add:hover {
    background: var(--primary-50);
    border-color: var(--primary-300);
    color: var(--primary-600);
    border-style: solid;
    transform: scale(1.05);
}

/* Button with ripple effect */
.btn-success::after, .btn-primary::after {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(circle, rgba(255,255,255,0.3) 0%, transparent 70%);
    transform: scale(0);
    opacity: 0;
    transition: transform 0.5s, opacity 0.3s;
}

.btn-success:active::after, .btn-primary:active::after {
    transform: scale(2);
    opacity: 1;
    transition: 0s;
}

/* ============================================
   7. CARDS
   ============================================ */

/* Group Card */
.group-card {
    position: relative;
    background: var(--surface);
    border-radius: var(--radius-xl);
    padding: 0;
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid var(--border);
    overflow: hidden;
    will-change: transform, box-shadow;
}

.group-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary-400), var(--accent-400));
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.group-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-200);
}

.group-card:hover::before {
    opacity: 1;
}

.group-card-header {
    position: absolute;
    top: var(--space-3);
    right: var(--space-3);
    z-index: 10;
}

.group-card-actions {
    display: flex;
    gap: var(--space-2);
    opacity: 0;
    transform: translateX(8px);
    transition: all var(--transition-fast);
}

.group-card:hover .group-card-actions {
    opacity: 1;
    transform: translateX(0);
}

.group-action-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: var(--text-sm);
    transition: all var(--transition-fast);
    color: var(--text-tertiary);
    box-shadow: var(--shadow-sm);
}

.group-action-btn:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

.group-action-btn.edit {
    transform: scaleX(-1);
}

.group-action-btn.edit:hover {
    background: var(--accent-50);
    border-color: var(--accent-300);
    color: var(--accent-600);
    transform: scaleX(-1) scale(1.1);
}

.group-action-btn.delete:hover {
    background: var(--danger-50);
    border-color: var(--danger-300);
    color: var(--danger-500);
}

.group-card-content {
    padding: var(--space-5);
    padding-top: var(--space-12);
    display: flex;
    flex-direction: column;
    gap: var(--space-4);
}

.group-card .group-info {
    flex: 1;
    min-width: 0;
}

.group-card .group-info h3 {
    font-size: var(--text-lg);
    color: var(--text-primary);
    margin-bottom: var(--space-2);
    word-break: break-word;
    font-weight: var(--font-bold);
    line-height: var(--leading-snug);
}

.group-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-3);
    color: var(--text-tertiary);
    font-size: var(--text-sm);
}

.group-meta span {
    display: inline-flex;
    align-items: center;
    gap: var(--space-1);
}

.group-amount {
    font-size: var(--text-2xl);
    font-weight: var(--font-bold);
    color: var(--primary-600);
    white-space: nowrap;
    letter-spacing: var(--tracking-tight);
    font-feature-settings: 'tnum';
    padding-top: var(--space-3);
    border-top: 1px solid var(--border-subtle);
    text-align: right;
}

/* ============================================
   8. TOTAL EXPENSES CARD
   ============================================ */

/* Total Expenses - Clean, Premium Design */
.total-expenses {
    margin: var(--space-6) 0;
    background: var(--surface);
    padding: var(--space-6);
    border-radius: var(--radius-xl);
    text-align: center;
    border: 1px solid var(--border);
    box-shadow: var(--shadow-lg);
}

.total-expenses h2 {
    font-size: var(--text-4xl);
    margin: 0 0 var(--space-1) 0;
    font-weight: var(--font-bold);
    letter-spacing: var(--tracking-tight);
    font-feature-settings: 'tnum';
    color: var(--primary-600);
}

.total-expenses p {
    margin: 0;
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: var(--tracking-wide);
}

/* ============================================
   9. GROUPS SECTION
   ============================================ */

.groups-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin: var(--space-8) 0 var(--space-6) 0;
    gap: var(--space-4);
    flex-wrap: wrap;
}

.groups-header h2 {
    font-size: var(--text-2xl);
    color: var(--text-primary);
    margin: 0;
    font-weight: var(--font-bold);
    letter-spacing: var(--tracking-tight);
}

.group-count {
    color: var(--text-tertiary);
    font-size: var(--text-sm);
    margin: var(--space-2) 0 0 0;
    font-weight: var(--font-medium);
    display: inline-flex;
    align-items: center;
    gap: var(--space-2);
}

.groups-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--space-5);
    margin-bottom: var(--space-8);
    align-items: start;
}

/* ============================================
   10. EXPENSE ITEMS - Stacked Layout
   ============================================ */

/*
 * STRUCTURE:
 * .expense-item (flex row)
 * ├── .expense-content (flex: 1, stacked vertically)
 * │   ├── h4 (title)
 * │   ├── .expense-amount (prominent, green)
 * │   ├── .expense-meta (paid by, split info)
 * │   └── .expense-date
 * └── .expense-actions (vertical buttons on right)
 */

.expenses-list {
    display: flex;
    flex-direction: column;
    gap: 0;
    margin-bottom: var(--space-6);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

/* Main container - clean line style */
.expense-item {
    position: relative;
    background: transparent;
    padding: var(--space-4) var(--space-4);
    border: none;
    border-bottom: 1px solid var(--border-subtle);
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: var(--space-4);
}

.expense-item:last-child {
    border-bottom: none;
}

/* Left accent bar - appears on hover */
.expense-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    height: 0;
    width: 3px;
    background: var(--primary-500);
    border-radius: 0 var(--radius-full) var(--radius-full) 0;
    transition: height var(--transition-base);
}

.expense-item:hover {
    background: var(--gray-50);
}

.expense-item:hover::before {
    height: 60%;
}

/* Content area - CSS Grid for two-column layout */
.expense-content {
    flex: 1;
    min-width: 0;
    display: grid;
    grid-template-columns: 1fr auto;
    grid-template-rows: auto auto;
    gap: var(--space-1) var(--space-4);
    align-items: baseline;
}

/* Title - top left */
.expense-content h4 {
    grid-column: 1;
    grid-row: 1;
    font-size: var(--text-base);
    font-weight: var(--font-bold);
    color: var(--text-primary);
    margin: 0;
    line-height: var(--leading-snug);
}

/* Amount - top right */
.expense-amount {
    grid-column: 2;
    grid-row: 1;
    font-size: var(--text-lg);
    font-weight: var(--font-bold);
    color: var(--primary-600);
    font-feature-settings: 'tnum';
    text-align: right;
    justify-self: end;
}

/* Per-person amount - bottom right (replaces date) */
.per-person-amount {
    grid-column: 2;
    grid-row: 2;
    font-size: var(--text-xs);
    font-weight: var(--font-medium);
    color: var(--text-secondary);
    text-align: right;
    justify-self: end;
    font-feature-settings: 'tnum';
}

/* Meta info - bottom left */
.expense-meta {
    grid-column: 1;
    grid-row: 2;
    color: var(--text-tertiary);
    font-size: var(--text-sm);
    line-height: var(--leading-relaxed);
}

/* Date - bottom right */
.expense-date {
    grid-column: 2;
    grid-row: 2;
    color: var(--text-tertiary);
    font-size: var(--text-xs);
    text-align: right;
}

/* Action buttons - vertical, centered on right */
.expense-actions {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    flex-shrink: 0;
    align-self: center;
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.expense-item:hover .expense-actions {
    opacity: 1;
}

.expense-action-btn {
    background: var(--gray-100);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: var(--text-sm);
    transition: all var(--transition-fast);
    color: var(--text-secondary);
}

.expense-action-btn:hover {
    transform: scale(1.05);
}

.expense-action-btn.edit {
    transform: scaleX(-1);
}

.expense-action-btn.edit:hover {
    background: var(--accent-100);
    border-color: var(--accent-300);
    color: var(--accent-600);
    transform: scaleX(-1) scale(1.05);
}

.expense-action-btn.delete:hover {
    background: var(--danger-100);
    border-color: var(--danger-300);
    color: var(--danger-500);
}

/* Mobile - stacked layout with clear typography hierarchy */
@media (max-width: 640px) {
    .expense-item::before {
        display: none;
    }
    
    .expense-item {
        padding: var(--space-4);
        align-items: flex-start;
        position: relative;
        flex-wrap: wrap;
        background: transparent;
        border-bottom: 1px solid var(--border-subtle);
    }
    
    .expense-item:last-child {
        border-bottom: none;
    }
    
    /* Stack everything vertically on mobile - full width */
    .expense-content {
        display: flex;
        flex-direction: column;
        gap: 2px;
        width: 100%;
        flex: 1 1 100%;
        order: 2;
        margin-top: var(--space-1);
    }
    
    /* Actions float at top right */
    .expense-item .expense-actions {
        position: absolute;
        top: var(--space-3);
        right: var(--space-3);
        opacity: 1;
        flex-direction: row;
    }
    
    /* Title - 17px, semibold, dark (with space for actions) */
    .expense-item .expense-content h4 {
        order: 1;
        font-size: 1.0625rem;
        font-weight: 600;
        color: var(--text-primary);
        margin: 0 0 2px 0;
        grid-column: auto;
        grid-row: auto;
        padding-right: 70px;
    }
    
    /* Amount - 18px, bold, green (prominent but balanced) */
    .expense-item .expense-amount {
        order: 2;
        text-align: left;
        font-size: 1.125rem;
        font-weight: 700;
        color: var(--primary-600);
        margin: 0 0 6px 0;
        grid-column: auto;
        grid-row: auto;
    }
    
    /* Per-person on mobile */
    .expense-item .per-person-amount {
        order: 4;
        text-align: left;
        font-size: 0.75rem;
        color: var(--text-tertiary);
        grid-column: auto;
        grid-row: auto;
    }
    
    /* Meta - 13px, medium gray, full width */
    .expense-item .expense-meta {
        order: 3;
        font-size: 0.8125rem;
        font-weight: 400;
        color: var(--text-secondary);
        line-height: 1.4;
        margin: 0;
        grid-column: auto;
        grid-row: auto;
        width: 100%;
    }
    
    /* Date - 11px, light gray (smallest, most subtle) */
    .expense-item .expense-date {
        order: 4;
        text-align: left;
        font-size: 0.6875rem;
        font-weight: 400;
        color: var(--text-tertiary);
        margin: 4px 0 0 0;
        grid-column: auto;
        grid-row: auto;
    }
}

/* Touch devices - always show actions */
@media (hover: none) and (pointer: coarse) {
    .expense-actions {
        opacity: 1;
    }
}

/* ============================================
   11. SETTLEMENTS & BALANCES
   ============================================ */

/* Responsive visibility utilities */
.hide-on-mobile {
    display: inline-flex;
}

.show-on-mobile-only {
    display: none;
}

@media (max-width: 640px) {
    .hide-on-mobile {
        display: none !important;
    }
    
    .show-on-mobile-only {
        display: block !important;
    }
}

.balances-section {
    margin-top: var(--space-8);
    margin-bottom: var(--space-2);
    padding-bottom: var(--space-4);
}

.balances-header {
    margin-bottom: var(--space-4);
}

.balances-header h3 {
    margin: 0;
    font-size: var(--text-xl);
    font-weight: var(--font-bold);
    color: var(--text-primary);
}

.settlements-header {
    margin-bottom: var(--space-4);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.settlements-header h4 {
    margin: 0;
    font-size: var(--text-sm);
    font-weight: var(--font-semibold);
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: var(--tracking-wide);
}

.settlements-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
}

.settlement-item {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: var(--space-4) var(--space-5);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.settlement-item::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: linear-gradient(180deg, var(--danger-400), var(--danger-300));
}

.settlement-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-md);
}

.settlement-content {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    flex: 1;
}

.settlement-from,
.settlement-to {
    display: flex;
    align-items: center;
    min-width: 80px;
}

.member-name {
    font-weight: var(--font-semibold);
    font-size: var(--text-base);
}

.member-name.debtor {
    color: var(--color-negative);
}

.member-name.creditor {
    color: var(--color-positive);
}

.settlement-arrow {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-2);
    flex: 1;
}

.arrow-icon {
    font-size: var(--text-xl);
    color: var(--text-tertiary);
    opacity: 0.5;
}

.settlement-amount {
    font-weight: var(--font-bold);
    color: var(--text-primary);
    font-size: var(--text-base);
    background: var(--gray-100);
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-full);
    font-feature-settings: 'tnum';
}

.settlement-actions {
    margin-left: var(--space-4);
}

.settlement-btn {
    background: linear-gradient(135deg, var(--success-500) 0%, var(--success-600) 100%);
    color: var(--text-inverse);
    border: none;
    border-radius: var(--radius-md);
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: var(--text-base);
    transition: all var(--transition-fast);
    box-shadow: var(--shadow-sm);
}

.settlement-btn:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

/* Settlement Complete */
.settlement-complete {
    text-align: center;
    padding: var(--space-12) var(--space-8);
    background: linear-gradient(135deg, var(--success-50) 0%, var(--primary-50) 100%);
    border-radius: var(--radius-2xl);
    border: 2px solid var(--success-200);
}

.settlement-icon {
    font-size: var(--text-5xl);
    margin-bottom: var(--space-4);
    line-height: 1;
}

.settlement-complete h4 {
    font-size: var(--text-xl);
    margin: 0 0 var(--space-2) 0;
    color: var(--success-700);
    font-weight: var(--font-bold);
}

.settlement-complete p {
    margin: 0;
    color: var(--text-secondary);
}

/* Balance Items */
.balances-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.balance-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-4) var(--space-5);
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    transition: all var(--transition-fast);
}

.balance-item:hover {
    background: var(--gray-50);
}

.balance-item.positive {
    border-left: 3px solid var(--success-400);
    background: linear-gradient(90deg, var(--success-50), var(--surface));
}

.balance-item.negative {
    border-left: 3px solid var(--danger-400);
    background: linear-gradient(90deg, var(--danger-50), var(--surface));
}

.balance-amount {
    font-weight: var(--font-bold);
    font-feature-settings: 'tnum';
}

.balance-item.positive .balance-amount {
    color: var(--success-600);
}

.balance-item.negative .balance-amount {
    color: var(--danger-500);
}

/* Individual Balances - Modern Style */
.individual-balances-list {
    display: flex;
    flex-direction: column;
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    overflow: hidden;
}

.balance-item-simple {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-4) var(--space-5);
    border-bottom: 1px solid var(--border-subtle);
    transition: background var(--transition-fast);
}

.balance-item-simple:last-child {
    border-bottom: none;
}

.balance-item-simple:hover {
    background: var(--gray-50);
}

.balance-name {
    font-weight: var(--font-medium);
    color: var(--text-primary);
    font-size: var(--text-base);
}

.balance-amount-simple {
    font-weight: var(--font-bold);
    font-size: var(--text-base);
    font-feature-settings: 'tnum';
}

.balance-amount-simple.receive {
    color: var(--success-600);
}

.balance-amount-simple.pay {
    color: var(--color-negative);
}

.balance-amount-simple.zero {
    color: var(--text-tertiary);
}

.balance-legend {
    display: flex;
    gap: var(--space-6);
    justify-content: center;
    margin-top: var(--space-6);
    padding-top: var(--space-4);
    border-top: 1px solid var(--border-subtle);
    font-size: var(--text-sm);
    color: var(--text-tertiary);
}

.legend-item {
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.legend-color {
    width: 12px;
    height: 12px;
    border-radius: var(--radius-full);
}

.legend-color.blue {
    background: var(--success-500);
}

.legend-color.red {
    background: var(--color-negative);
}

/* Modern Settlements List */
.settlements-list-modern {
    display: flex;
    flex-direction: column;
    background: var(--surface);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    overflow: hidden;
}

.settlement-item-modern {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4);
    border-bottom: 1px solid var(--border-subtle);
    transition: background var(--transition-fast);
    position: relative;
}

.settlement-item-modern::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: var(--color-negative);
}

.settlement-item-modern:last-child {
    border-bottom: none;
}

.settlement-item-modern:hover {
    background: var(--gray-50);
}

.settlement-info {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    flex: 1;
}

.settlement-from-name {
    font-weight: var(--font-semibold);
    color: var(--color-negative);
    font-size: var(--text-base);
}

.settlement-arrow-modern {
    color: var(--text-tertiary);
    font-size: var(--text-base);
    opacity: 0.6;
}

.settlement-to-name {
    font-weight: var(--font-semibold);
    color: var(--success-600);
    font-size: var(--text-base);
}

.settlement-amount-modern {
    font-weight: var(--font-bold);
    color: var(--text-primary);
    font-size: var(--text-base);
    margin-left: auto;
    font-feature-settings: 'tnum';
}

/* ============================================
   12. EMPTY STATES
   ============================================ */

.empty-state {
    text-align: center;
    padding: var(--space-16) var(--space-6);
    color: var(--text-secondary);
    background: linear-gradient(180deg, var(--gray-50) 0%, transparent 100%);
    border-radius: var(--radius-2xl);
    border: 2px dashed var(--border);
    margin: var(--space-8) 0;
    animation: fadeIn 0.5s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.empty-state::before {
    content: '';
    display: block;
    width: 120px;
    height: 120px;
    margin: 0 auto var(--space-6);
    background: url('../images/logo.png') center/contain no-repeat;
    animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

.empty-state p {
    font-size: var(--text-lg);
    margin-bottom: var(--space-2);
    color: var(--text-secondary);
    font-weight: var(--font-medium);
    line-height: var(--leading-relaxed);
}

.empty-state p:first-of-type {
    font-size: var(--text-xl);
    color: var(--text-primary);
    font-weight: var(--font-semibold);
    margin-bottom: var(--space-2);
}

.empty-state p:last-of-type {
    margin-bottom: var(--space-6);
    font-size: var(--text-base);
    color: var(--text-tertiary);
}

.empty-state .btn-success {
    margin-top: var(--space-4);
}

/* No settlements empty state */
.no-settlements, .no-balances {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: var(--space-10) var(--space-6);
    color: var(--text-tertiary);
    font-style: normal;
}

/* ============================================
   13. MODALS
   ============================================ */

.modal {
    display: none;
    position: fixed;
    z-index: var(--z-modal-backdrop);
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(15, 23, 42, 0.5);
    backdrop-filter: blur(4px);
    overflow-y: auto;
    padding: var(--space-6);
    animation: modalBackdropIn 0.2s ease-out;
}

@keyframes modalBackdropIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.modal-content {
    background-color: var(--surface);
    margin: 0 auto;
    border-radius: var(--radius-2xl);
    width: 100%;
    max-width: 480px;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
    box-shadow: var(--shadow-2xl);
    border: 1px solid var(--border);
    animation: modalSlideIn 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes modalSlideIn {
    from { 
        opacity: 0; 
        transform: translateY(-20px) scale(0.95);
    }
    to { 
        opacity: 1; 
        transform: translateY(0) scale(1);
    }
}

.modal-header {
    padding: var(--space-5) var(--space-6);
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--surface);
    border-radius: var(--radius-2xl) var(--radius-2xl) 0 0;
}

.modal-header h3 {
    margin: 0;
    color: var(--text-primary);
    font-size: var(--text-lg);
    font-weight: var(--font-semibold);
}

.close {
    font-size: var(--text-2xl);
    color: var(--text-tertiary);
    cursor: pointer;
    padding: var(--space-1) var(--space-2);
    line-height: 1;
    transition: all var(--transition-fast);
    font-weight: var(--font-light);
    border-radius: var(--radius-md);
}

.close:hover {
    color: var(--text-primary);
    background: var(--gray-100);
}

.modal-body {
    padding: var(--space-6);
    background: var(--surface);
}

.modal-footer {
    padding: var(--space-4) var(--space-6);
    border-top: 1px solid var(--border-subtle);
    display: flex;
    gap: var(--space-3);
    justify-content: flex-end;
    background: var(--gray-50);
    border-radius: 0 0 var(--radius-2xl) var(--radius-2xl);
}

/* Snapshot Preview Styles */
.snapshot-preview {
    background: var(--gray-100);
    border-radius: var(--radius-lg);
    padding: var(--space-3);
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border-subtle);
}

.snapshot-preview .snapshot-loading,
.snapshot-preview .snapshot-error {
    color: var(--text-tertiary);
    font-size: var(--text-sm);
    margin: 0;
}

.snapshot-preview .snapshot-error {
    color: var(--error-600);
}

.snapshot-preview .snapshot-image {
    max-width: 100%;
    max-height: 300px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
}


.modal-footer-with-delete {
    padding: var(--space-4) var(--space-6);
    border-top: 1px solid var(--border-subtle);
    display: flex;
    gap: var(--space-3);
    justify-content: space-between;
    align-items: center;
    background: var(--gray-50);
    border-radius: 0 0 var(--radius-2xl) var(--radius-2xl);
}

.modal-footer-left {
    flex-shrink: 0;
}

.modal-footer-right {
    display: flex;
    gap: var(--space-3);
}

/* ============================================
   14. FORMS
   ============================================ */

.form-group {
    margin-bottom: var(--space-5);
}

.form-group label {
    display: block;
    margin-bottom: var(--space-2);
    font-weight: var(--font-medium);
    color: var(--text-primary);
    font-size: var(--text-sm);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    font-size: var(--text-base);
    transition: all var(--transition-fast);
    min-height: 44px;
    background: var(--surface);
    color: var(--text-primary);
    font-family: inherit;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-400);
    box-shadow: 0 0 0 3px var(--primary-100);
}

.form-group input::placeholder {
    color: var(--text-tertiary);
}

.form-group input.invalid,
.form-group input:invalid:not(:placeholder-shown) {
    border-color: var(--danger-400);
    background-color: var(--danger-50);
}

.form-group input.invalid:focus,
.form-group input:invalid:not(:placeholder-shown):focus {
    border-color: var(--danger-400);
    box-shadow: 0 0 0 3px var(--danger-100);
}

.form-help {
    font-size: var(--text-sm);
    color: var(--text-tertiary);
    margin-top: var(--space-2);
}

.form-help.success {
    color: var(--success-600);
}

.form-help.error {
    color: var(--danger-500);
}

.form-help.warning {
    color: var(--warning-600);
}

.form-help-text {
    margin-top: var(--space-1);
    font-size: var(--text-xs);
    color: var(--text-tertiary);
}

/* Selection Container */
.selection-container {
    background: var(--gray-50);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-4);
}

.selection-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-4);
    flex-wrap: wrap;
    gap: var(--space-2);
}

.selection-header span {
    font-weight: var(--font-medium);
    color: var(--text-secondary);
    font-size: var(--text-sm);
}

.selection-actions {
    display: flex;
    gap: var(--space-4);
}

.selection-action {
    color: var(--primary-600);
    text-decoration: none;
    cursor: pointer;
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    padding: var(--space-1) 0;
    border: none;
    background: none;
    transition: color var(--transition-fast);
}

.selection-action:hover {
    color: var(--primary-700);
    text-decoration: underline;
}

.selectable-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: var(--space-3);
    margin-bottom: var(--space-4);
}

.selectable-box {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: var(--space-3) var(--space-2);
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    min-height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    color: var(--text-primary);
}

.selectable-box:hover {
    border-color: var(--primary-300);
    background: var(--primary-50);
    transform: translateY(-2px);
}

.selectable-box.selected {
    border-color: var(--primary-500);
    background: linear-gradient(135deg, var(--primary-500) 0%, var(--primary-600) 100%);
    color: var(--text-inverse);
    font-weight: var(--font-semibold);
    box-shadow: var(--shadow-sm), var(--shadow-primary);
}

.selectable-box.selected::after {
    content: '✓';
    position: absolute;
    top: -6px;
    right: -6px;
    background: var(--success-500);
    color: var(--text-inverse);
    border-radius: var(--radius-full);
    width: 18px;
    height: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 10px;
    font-weight: var(--font-bold);
    border: 2px solid var(--surface);
    box-shadow: var(--shadow-sm);
}

/* Add Item Section */
.add-item-section {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3);
    background: var(--surface);
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
}

.add-item-input {
    flex: 1;
    border: none;
    background: none;
    font-size: var(--text-base);
    padding: var(--space-2) 0;
    color: var(--text-primary);
}

.add-item-input:focus {
    outline: none;
}

.add-item-input::placeholder {
    color: var(--text-tertiary);
}

/* Dynamic Items */
.dynamic-items {
    margin-top: var(--space-3);
}

.dynamic-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-3) var(--space-4);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    margin-bottom: var(--space-2);
}

.dynamic-item-content {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    flex: 1;
}

.dynamic-item-name {
    flex: 1;
    font-size: var(--text-base);
    color: var(--text-primary);
}

.dynamic-item-actions {
    display: flex;
    gap: var(--space-2);
}

.icon-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    cursor: pointer;
    padding: 0;
    border-radius: var(--radius-md);
    color: var(--text-tertiary);
    font-size: var(--text-base);
    transition: all var(--transition-fast);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    transform: translateY(-1px);
}

.icon-btn.edit:hover {
    background: var(--accent-50);
    border-color: var(--accent-300);
    color: var(--accent-600);
}

.icon-btn.delete:hover {
    background: var(--danger-50);
    border-color: var(--danger-300);
    color: var(--danger-500);
}

/* ============================================
   15. TABS
   ============================================ */

.tab-navigation {
    display: flex;
    gap: var(--space-1);
    margin: var(--space-6) 0 var(--space-5) 0;
    background: var(--gray-100);
    border-radius: var(--radius-lg);
    padding: var(--space-1);
}

.tab-btn {
    flex: 1;
    padding: var(--space-3) var(--space-5);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    cursor: pointer;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    text-align: center;
    white-space: nowrap;
}

.tab-btn:hover {
    color: var(--text-primary);
}

.tab-btn.active {
    background: var(--surface);
    color: var(--primary-600);
    font-weight: var(--font-semibold);
    box-shadow: var(--shadow-sm);
}

.tab-content {
    display: none;
    animation: tabFadeIn 0.3s ease-out;
}

.tab-content.active {
    display: block;
}

@keyframes tabFadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ============================================
   16. NOTIFICATIONS
   ============================================ */

.notification {
    position: fixed;
    top: var(--space-5);
    right: var(--space-5);
    padding: var(--space-4) var(--space-5);
    border-radius: var(--radius-lg);
    color: var(--text-inverse);
    font-weight: var(--font-medium);
    z-index: var(--z-notification);
    max-width: 380px;
    box-shadow: var(--shadow-xl);
    animation: notificationSlideIn 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

@keyframes notificationSlideIn {
    from { 
        opacity: 0; 
        transform: translateX(100%);
    }
    to { 
        opacity: 1; 
        transform: translateX(0);
    }
}

.notification.success {
    background: linear-gradient(135deg, var(--success-500) 0%, var(--success-600) 100%);
}

.notification.error {
    background: linear-gradient(135deg, var(--danger-400) 0%, var(--danger-500) 100%);
}

.notification.info {
    background: linear-gradient(135deg, var(--accent-500) 0%, var(--accent-600) 100%);
}

.notification.warning {
    background: linear-gradient(135deg, var(--warning-500) 0%, var(--warning-600) 100%);
}

/* ============================================
   17. LOADING STATES
   ============================================ */

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--gray-200);
    border-top: 3px solid var(--primary-500);
    border-radius: var(--radius-full);
    animation: spin 0.8s linear infinite;
    margin: var(--space-4) auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Loading screen: no black bg, logo clear and not compressed */
.loading-screen {
    background: linear-gradient(135deg, #f8fafc 0%, #ecfdf5 100%) !important;
}
.loading-screen .loading-logo-wrap {
    background: transparent !important;
    border: none !important;
    border-radius: 0 !important;
    box-shadow: none !important;
}
.loading-screen .loading-logo-img {
    object-fit: contain;
    image-rendering: auto;
}

/* Skeleton loading */
.skeleton {
    background: linear-gradient(90deg, var(--gray-200) 25%, var(--gray-100) 50%, var(--gray-200) 75%);
    background-size: 200% 100%;
    animation: shimmerSkeleton 1.5s infinite;
    border-radius: var(--radius-md);
}

@keyframes shimmerSkeleton {
    0% { background-position: 200% 0; }
    100% { background-position: -200% 0; }
}

/* ============================================
   18. UTILITY CLASSES
   ============================================ */

.text-center { text-align: center; }
.text-success { color: var(--success-600); }
.text-danger { color: var(--danger-500); }
.text-muted { color: var(--text-tertiary); }
.d-none { display: none; }
.d-block { display: block; }
.w-100 { width: 100%; }

/* ============================================
   19. ACCESSIBILITY
   ============================================ */

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}

/* Focus styles */
button:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
.selectable-box:focus-visible,
a:focus-visible {
    outline: 2px solid var(--primary-500);
    outline-offset: 2px;
}

/* Remove focus outline from main app content */
#mainAppContent:focus {
    outline: none;
}

/* High contrast mode */
@media (prefers-contrast: high) {
    :root {
        --border: var(--gray-400);
    }
    
    .selectable-box {
        border-width: 2px;
    }
    
    .btn-success, .btn-primary {
        border: 2px solid transparent;
    }
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ============================================
   20. CUSTOM AMOUNTS (UNEQUAL SPLITS)
   ============================================ */

.custom-amounts-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-3);
    font-size: var(--text-sm);
    font-weight: var(--font-semibold);
    color: var(--text-secondary);
}

.custom-amounts-total {
    font-weight: var(--font-bold);
    color: var(--primary-600);
    font-feature-settings: 'tnum';
}

.custom-amounts-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-3);
}

.custom-amount-item {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3);
    background: var(--surface);
    border-radius: var(--radius-md);
    border: 1px solid var(--border);
}

.custom-amount-item label {
    flex: 0 0 100px;
    font-weight: var(--font-medium);
    color: var(--text-primary);
    font-size: var(--text-sm);
    margin: 0;
}

.custom-amount-input {
    flex: 1;
    padding: var(--space-2) var(--space-3);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: var(--text-sm);
    font-weight: var(--font-semibold);
    background: var(--surface);
    color: var(--text-primary);
    transition: all var(--transition-fast);
    font-feature-settings: 'tnum';
}

.custom-amount-input:focus {
    outline: none;
    border-color: var(--primary-400);
    box-shadow: 0 0 0 3px var(--primary-100);
}

/* ============================================
   21. USER AUTHENTICATION
   ============================================ */

.previous-users-section {
    margin-bottom: var(--space-6);
}

.previous-users-list {
    max-height: 280px;
    overflow-y: auto;
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    background: var(--gray-50);
}

.previous-user-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-4);
    border-bottom: 1px solid var(--border-subtle);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.previous-user-item:hover {
    background: var(--gray-100);
}

.previous-user-item:last-child {
    border-bottom: none;
}

.user-name {
    font-weight: var(--font-semibold);
    color: var(--text-primary);
    font-size: var(--text-base);
}

.user-id {
    font-size: var(--text-sm);
    color: var(--text-tertiary);
    margin: var(--space-1) 0;
}

.last-used {
    font-size: var(--text-xs);
    color: var(--text-tertiary);
}

.btn-remove {
    background: var(--danger-100);
    color: var(--danger-600);
    border: none;
    border-radius: var(--radius-full);
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: var(--text-lg);
    transition: all var(--transition-fast);
}

.btn-remove:hover {
    background: var(--danger-200);
    color: var(--danger-700);
    transform: scale(1.1);
}

.input-with-status {
    display: flex;
    gap: var(--space-2);
    align-items: center;
}

.input-with-status input {
    flex: 1;
}

.btn-check {
    background: var(--accent-500);
    color: var(--text-inverse);
    border: none;
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn-check:hover:not(:disabled) {
    background: var(--accent-600);
}

.btn-check:disabled {
    background: var(--gray-300);
    cursor: not-allowed;
}

.no-users {
    text-align: center;
    padding: var(--space-8);
    color: var(--text-tertiary);
    font-style: italic;
}

.new-user-form {
    margin-top: var(--space-4);
}

/* ============================================
   22. DETAILS VIEW
   ============================================ */

.details-view {
    padding: var(--space-6) 0;
    padding-top: var(--header-height);
    min-height: 100vh;
    background: var(--background);
}

.details-view-back {
    background: var(--surface);
    padding: var(--space-4) 0;
    position: sticky;
    top: 0;
    z-index: var(--z-sticky);
    box-shadow: var(--shadow-sm);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: var(--space-6) 0 var(--space-4) 0;
}

.section-header h3 {
    font-size: var(--text-lg);
    color: var(--text-primary);
    margin: 0;
    font-weight: var(--font-semibold);
}

/* Settlement Details */
.settlement-details {
    margin-top: var(--space-8);
    padding-top: var(--space-8);
    border-top: 1px solid var(--border);
}

.settlement-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-5);
}

.settlement-header h4 {
    margin: 0;
    font-size: var(--text-lg);
    font-weight: var(--font-semibold);
    color: var(--text-primary);
}

.btn-link-small {
    background: none;
    border: none;
    color: var(--danger-500);
    font-size: var(--text-sm);
    font-weight: var(--font-medium);
    cursor: pointer;
    padding: var(--space-1) var(--space-2);
}

.btn-link-small:hover {
    text-decoration: underline;
}

/* Total Expense Summary */
.total-expense-summary {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-5) var(--space-6);
    margin-top: var(--space-6);
    border-top: 2px solid var(--border);
    background: var(--gray-50);
    border-radius: var(--radius-lg);
}

.total-label {
    color: var(--text-primary);
    font-size: var(--text-base);
    font-weight: var(--font-semibold);
}

.total-amount {
    color: var(--primary-600);
    font-size: var(--text-lg);
    font-weight: var(--font-bold);
    font-feature-settings: 'tnum';
}

/* Expense List - Simple Style */
.expense-item-simple {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-4) var(--space-5);
    border-bottom: 1px solid var(--border-subtle);
    transition: background var(--transition-fast);
}

.expense-item-simple:hover {
    background: var(--gray-50);
}

.expense-item-simple:last-child {
    border-bottom: none;
}

.expense-item-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex: 1;
    gap: var(--space-4);
}

.expense-name {
    font-weight: var(--font-medium);
    color: var(--text-primary);
    font-size: var(--text-base);
}

.expense-amount-simple {
    font-weight: var(--font-semibold);
    color: var(--text-primary);
    font-size: var(--text-base);
    font-feature-settings: 'tnum';
}

.expense-actions-simple {
    display: flex;
    gap: var(--space-2);
    margin-left: var(--space-4);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.expense-item-simple:hover .expense-actions-simple {
    opacity: 1;
}

/* Danger Zone */
.danger-zone {
    margin-top: var(--space-8);
    padding-top: var(--space-6);
    border-top: 1px solid var(--danger-200);
}

/* ============================================
   23. SEARCH
   ============================================ */

.search-box {
    position: relative;
    flex: 0 1 260px;
}

.search-box input {
    width: 100%;
    padding: var(--space-3) var(--space-4) var(--space-3) var(--space-10);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    font-size: var(--text-sm);
    background: var(--surface);
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary-400);
    box-shadow: 0 0 0 3px var(--primary-100);
}

.search-box::before {
    content: '🔍';
    position: absolute;
    left: var(--space-3);
    top: 50%;
    transform: translateY(-50%);
    font-size: var(--text-sm);
    pointer-events: none;
    opacity: 0.5;
}

/* ============================================
   24. MOBILE RESPONSIVE
   ============================================ */

/* Desktop: ensure app uses full width and doesn't get mobile layout */
@media (min-width: 769px) {
    .app-wrapper,
    #mainAppContent {
        width: 100%;
        max-width: 100%;
    }
    .app-wrapper > main.container {
        max-width: 1200px;
    }
}

@media (max-width: 768px) {
    /* Typography */
    h1 { font-size: var(--text-2xl); }
    h2 { font-size: var(--text-xl); }
    h3 { font-size: var(--text-lg); }
    
    body {
        font-size: var(--text-sm);
    }
    
    /* Container */
    .container {
        padding: 0 var(--space-4);
    }
    
    /* Header */
    header {
        padding: var(--space-3) 0;
    }
    
    .logo h1 {
        font-size: var(--text-lg);
    }
    
    .logo p {
        font-size: 10px;
    }
    
    .user-info {
        gap: var(--space-2);
    }
    
    #currentUserName {
        font-size: var(--text-sm);
    }
    
    /* Group Header - stacked on mobile; main content needs extra top padding */
    .group-header + main {
        padding-top: 10rem;
    }
    
    .group-header .container {
        flex-direction: column;
        align-items: stretch;
        gap: var(--space-3);
    }
    
    .group-header-left {
        gap: var(--space-2);
    }
    
    .group-info h1 {
        font-size: var(--text-lg);
    }
    
    .group-actions {
        justify-content: space-between;
        width: 100%;
    }
    
    .group-actions .btn-secondary,
    .group-actions .btn-success {
        flex: 1;
        padding: var(--space-3) var(--space-4);
    }
    
    /* Groups */
    .groups-header {
        flex-direction: column;
        align-items: stretch;
        gap: var(--space-4);
        margin: var(--space-6) 0 var(--space-4) 0;
    }
    
    .groups-list {
        grid-template-columns: 1fr;
        gap: var(--space-4);
    }
    
    .group-card-content {
        padding: var(--space-4);
        padding-top: var(--space-10);
        gap: var(--space-3);
    }
    
    .group-amount {
        font-size: var(--text-xl);
    }
    
    .group-card-actions {
        opacity: 1;
        transform: translateX(0);
    }
    
    /* Total Expenses - clear of fixed header on mobile */
    .group-header + main .total-expenses {
        scroll-margin-top: 8.5rem;
    }
    
    .total-expenses {
        padding: var(--space-5);
        margin: var(--space-4) 0;
    }
    
    .total-expenses h2 {
        font-size: var(--text-2xl);
    }
    
    /* Buttons */
    .btn-primary, .btn-success, .btn-secondary, .btn-danger {
        width: 100%;
        justify-content: center;
        padding: var(--space-4);
    }
    
    /* Section Header */
    .section-header {
        flex-direction: column;
        align-items: stretch;
        gap: var(--space-3);
    }
    
    /* Note: Expense item responsive styles are in section 10b */
    
    /* Settlement Items */
    .settlement-item {
        padding: var(--space-4);
        flex-direction: column;
        gap: var(--space-4);
    }
    
    .settlement-content {
        flex-direction: column;
        gap: var(--space-3);
        width: 100%;
        text-align: center;
    }
    
    .settlement-arrow {
        flex-direction: row;
    }
    
    .arrow-icon {
        transform: rotate(90deg);
    }
    
    .settlement-actions {
        margin-left: 0;
    }
    
    .settlement-item-modern {
        padding: var(--space-3);
        flex-wrap: wrap;
    }
    
    /* Modal */
    .modal {
        padding: var(--space-4);
    }
    
    .modal-content {
        max-height: 95vh;
        margin-top: var(--space-4);
    }
    
    .modal-footer {
        flex-direction: column-reverse;
        gap: var(--space-3);
    }
    
    .modal-footer .btn-secondary,
    .modal-footer .btn-success {
        width: 100%;
        padding: 12px 16px;
        font-size: 15px;
    }
    
    .modal-footer-with-delete {
        flex-direction: column;
        gap: var(--space-3);
    }
    
    .modal-footer-left,
    .modal-footer-right {
        width: 100%;
    }
    
    .modal-footer-right {
        flex-direction: column-reverse;
    }
    
    /* Share Modal - Mobile */
    .snapshot-preview {
        padding: var(--space-2);
    }
    
    .snapshot-preview .snapshot-image {
        max-height: 250px;
    }
    
    /* Selectable Grid */
    .selectable-grid {
        grid-template-columns: 1fr 1fr;
        gap: var(--space-2);
    }
    
    /* Details view – clear fixed header + tab bar on mobile */
    .details-view {
        padding-top: calc(var(--header-height) + 4.5rem);
    }

    /* Tabs */
    .tab-navigation {
        margin: var(--space-4) 0;
    }
    
    .tab-btn {
        padding: var(--space-3);
        font-size: var(--text-sm);
    }
    
    /* Balance Items */
    .balance-item-simple,
    .expense-item-simple {
        padding: var(--space-3) var(--space-4);
    }
    
    .total-expense-summary {
        padding: var(--space-4);
        flex-direction: column;
        align-items: flex-start;
        gap: var(--space-2);
    }
    
    .balance-legend {
        flex-direction: column;
        gap: var(--space-3);
        align-items: center;
    }
    
    /* Empty State */
    .empty-state {
        padding: var(--space-10) var(--space-4);
    }
    
    .empty-state::before {
        width: 96px;
        height: 96px;
    }
    
    /* Notification */
    .notification {
        right: var(--space-3);
        left: var(--space-3);
        top: var(--space-3);
        max-width: none;
    }
    
    /* Custom Amounts */
    .custom-amount-item {
        flex-direction: column;
        align-items: stretch;
    }
    
    .custom-amount-item label {
        flex: none;
    }
    
    /* Input with status */
    .input-with-status {
        flex-direction: column;
        align-items: stretch;
    }
    
    .btn-check {
        margin-top: var(--space-2);
    }
}

/* Extra small screens */
@media (max-width: 400px) {
    .group-actions .btn-secondary,
    .group-actions .btn-success {
        padding: var(--space-3) var(--space-2);
        font-size: var(--text-sm);
    }
    
    .modal-footer-with-delete .btn-danger,
    .modal-footer-right .btn-secondary,
    .modal-footer-right .btn-success {
        padding: var(--space-3) var(--space-2);
        font-size: var(--text-sm);
    }
}

/* Touch device optimizations */
@media (hover: none) and (pointer: coarse) {
    .group-card-actions,
    .expense-actions,
    .expense-actions-simple {
        opacity: 1;
    }
    
    .group-action-btn,
    .expense-action-btn {
        width: 40px;
        height: 40px;
    }
}

/* Safe area handling for iOS */
@supports (padding: max(0px)) {
    .group-header {
        padding-left: max(var(--space-4), env(safe-area-inset-left));
        padding-right: max(var(--space-4), env(safe-area-inset-right));
    }
    
    .container {
        padding-left: max(var(--space-4), env(safe-area-inset-left));
        padding-right: max(var(--space-4), env(safe-area-inset-right));
    }
}

/* ============================================
   25. SCROLLBAR
   ============================================ */

/* Custom thin scrollbar — desktop only */
@media (min-width: 769px) {
    ::-webkit-scrollbar { width: 6px; height: 6px; }
    ::-webkit-scrollbar-track { background: transparent; }
    ::-webkit-scrollbar-thumb {
        background: var(--gray-300);
        border-radius: 99px;
        transition: background 0.2s;
    }
    ::-webkit-scrollbar-thumb:hover { background: var(--primary-400); }
    ::-webkit-scrollbar-corner { background: transparent; }
    body {
        scrollbar-width: thin;
        scrollbar-color: var(--gray-300) transparent;
    }
}

/* Hide scrollbar on mobile */
@media (max-width: 768px) {
    ::-webkit-scrollbar { display: none; width: 0; height: 0; }
    body { scrollbar-width: none; -ms-overflow-style: none; }
}

/* ============================================
   26. PRINT STYLES
   ============================================ */

@media print {
    header, .btn-success, .btn-secondary, .btn-danger,
    .group-card-actions, .expense-actions, .settlement-btn {
        display: none !important;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .group-card, .expense-item, .settlement-item {
        box-shadow: none;
        border: 1px solid #ccc;
    }
}