/* ============================================
   StudyFlow - Premium Study Management App
   Design System & Styles
   ============================================ */

/* CSS Variables - Alpine Frost Theme */
:root {
    /* Primary Colors */
    --color-primary: #2E5090;
    --color-primary-light: #4A7FD4;
    --color-primary-dark: #1A3A6E;
    --color-primary-gradient: linear-gradient(135deg, #2E5090 0%, #4A7FD4 100%);
    
    /* Background Colors */
    --color-bg-primary: #FFFFFF;
    --color-bg-secondary: #F8FAFC;
    --color-bg-tertiary: #F1F5F9;
    --color-bg-elevated: #FFFFFF;
    
    /* Text Colors */
    --color-text-primary: #0F172A;
    --color-text-secondary: #475569;
    --color-text-tertiary: #94A3B8;
    --color-text-inverse: #FFFFFF;
    
    /* Accent Colors */
    --color-accent-blue: #3B82F6;
    --color-accent-green: #10B981;
    --color-accent-amber: #F59E0B;
    --color-accent-rose: #F43F5E;
    --color-accent-purple: #8B5CF6;
    --color-accent-cyan: #06B6D4;
    
    /* Status Colors */
    --color-success: #10B981;
    --color-warning: #F59E0B;
    --color-error: #EF4444;
    --color-info: #3B82F6;
    
    /* Border & Shadow */
    --color-border: #E2E8F0;
    --color-border-light: #F1F5F9;
    --shadow-sm: 0 1px 2px 0 rgba(15, 23, 42, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.08), 0 2px 4px -2px rgba(15, 23, 42, 0.04);
    --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.04);
    --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.08), 0 8px 10px -6px rgba(15, 23, 42, 0.04);
    --shadow-glow: 0 0 20px rgba(46, 80, 144, 0.15);
    
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-2xl: 24px;
    --radius-full: 9999px;
    
    /* Typography */
    --font-display: 'Plus Jakarta Sans', sans-serif;
    --font-body: 'Inter', sans-serif;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-spring: 400ms cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* Layout */
    --bottom-nav-height: 72px;
    --safe-area-bottom: env(safe-area-inset-bottom, 0px);
    --header-height: 64px;
}

/* Dark Mode */
[data-theme="dark"] {
    --color-bg-primary: #0A0F1A;
    --color-bg-secondary: #111827;
    --color-bg-tertiary: #1E293B;
    --color-bg-elevated: #1E293B;
    
    --color-text-primary: #F8FAFC;
    --color-text-secondary: #94A3B8;
    --color-text-tertiary: #64748B;
    
    --color-border: #334155;
    --color-border-light: #1E293B;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 8px 10px -6px rgba(0, 0, 0, 0.3);
}

/* ============================================
   Base Styles
   ============================================ */

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-tap-highlight-color: transparent;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-body);
    background-color: var(--color-bg-secondary);
    color: var(--color-text-primary);
    line-height: 1.5;
    min-height: 100vh;
    overflow-x: hidden;
}

#app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ============================================
   Typography
   ============================================ */

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-display);
    font-weight: 700;
    line-height: 1.2;
    color: var(--color-text-primary);
}

h1 { font-size: 1.75rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.125rem; }
h5 { font-size: 1rem; }
h6 { font-size: 0.875rem; }

.text-display {
    font-family: var(--font-display);
    font-weight: 800;
}

.text-body {
    font-family: var(--font-body);
}

.text-sm { font-size: 0.875rem; }
.text-xs { font-size: 0.75rem; }
.text-lg { font-size: 1.125rem; }
.text-xl { font-size: 1.25rem; }

.font-medium { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }

.text-secondary { color: var(--color-text-secondary); }
.text-tertiary { color: var(--color-text-tertiary); }
.text-primary { color: var(--color-primary); }

/* ============================================
   Main Content Area
   ============================================ */

.main-content {
    flex: 1;
    padding: var(--space-4);
    padding-bottom: calc(var(--bottom-nav-height) + var(--safe-area-bottom) + var(--space-4));
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
}

.view {
    animation: fadeIn 0.3s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ============================================
   Bottom Navigation
   ============================================ */

.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    height: calc(var(--bottom-nav-height) + var(--safe-area-bottom));
    background: var(--color-bg-elevated);
    border-top: 1px solid var(--color-border);
    display: flex;
    justify-content: space-around;
    align-items: flex-start;
    padding-top: var(--space-2);
    padding-bottom: var(--safe-area-bottom);
    z-index: 100;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-1);
    padding: var(--space-2) var(--space-3);
    background: none;
    border: none;
    color: var(--color-text-tertiary);
    cursor: pointer;
    transition: color var(--transition-fast);
    position: relative;
}

.nav-item.active {
    color: var(--color-primary);
}

.nav-item::after {
    content: '';
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%) scale(0);
    width: 4px;
    height: 4px;
    background: var(--color-primary);
    border-radius: var(--radius-full);
    transition: transform var(--transition-spring);
}

.nav-item.active::after {
    transform: translateX(-50%) scale(1);
}

.nav-icon {
    width: 24px;
    height: 24px;
    transition: transform var(--transition-spring);
}

.nav-item.active .nav-icon {
    transform: translateY(-2px);
}

.nav-label {
    font-size: 0.6875rem;
    font-weight: 500;
    font-family: var(--font-display);
}

/* ============================================
   Bento Grid System
   ============================================ */

.bento-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-3);
    max-width: 600px;
    margin: 0 auto;
}

.bento-card {
    background: var(--color-bg-elevated);
    border-radius: var(--radius-xl);
    padding: var(--space-4);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border-light);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
    position: relative;
    overflow: hidden;
}

.bento-card:active {
    transform: scale(0.98);
}

.bento-card:hover {
    box-shadow: var(--shadow-md);
}

/* Card Sizes */
.bento-card.large {
    grid-column: span 2;
}

.bento-card.medium {
    grid-column: span 1;
    min-height: 140px;
}

.bento-card.small {
    grid-column: span 1;
    min-height: 100px;
}

.bento-card.full-width {
    grid-column: span 2;
}

/* Card Header */
.card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-3);
}

.card-title {
    font-family: var(--font-display);
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.card-icon {
    width: 32px;
    height: 32px;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg-tertiary);
}

.card-icon svg {
    width: 18px;
    height: 18px;
}

/* Card Content */
.card-content {
    position: relative;
    z-index: 1;
}

.card-value {
    font-family: var(--font-display);
    font-size: 1.75rem;
    font-weight: 800;
    color: var(--color-text-primary);
    line-height: 1.2;
}

.card-value.small {
    font-size: 1.25rem;
}

.card-label {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin-top: var(--space-1);
}

/* Gradient Backgrounds */
.card-gradient-blue {
    background: linear-gradient(135deg, #2E5090 0%, #4A7FD4 100%);
    color: white;
}

.card-gradient-blue .card-title,
.card-gradient-blue .card-value,
.card-gradient-blue .card-label {
    color: white;
}

.card-gradient-purple {
    background: linear-gradient(135deg, #7C3AED 0%, #A78BFA 100%);
    color: white;
}

.card-gradient-purple .card-title,
.card-gradient-purple .card-value,
.card-gradient-purple .card-label {
    color: white;
}

.card-gradient-amber {
    background: linear-gradient(135deg, #F59E0B 0%, #FBBF24 100%);
    color: white;
}

.card-gradient-amber .card-title,
.card-gradient-amber .card-value,
.card-gradient-amber .card-label {
    color: white;
}

.card-gradient-rose {
    background: linear-gradient(135deg, #F43F5E 0%, #FB7185 100%);
    color: white;
}

.card-gradient-rose .card-title,
.card-gradient-rose .card-value,
.card-gradient-rose .card-label {
    color: white;
}

/* ============================================
   Progress Circle
   ============================================ */

.progress-circle {
    position: relative;
    width: 80px;
    height: 80px;
    margin: 0 auto;
}

.progress-circle svg {
    transform: rotate(-90deg);
    width: 100%;
    height: 100%;
}

.progress-circle-bg {
    fill: none;
    stroke: var(--color-bg-tertiary);
    stroke-width: 8;
}

.progress-circle-fill {
    fill: none;
    stroke: var(--color-primary);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 220;
    stroke-dashoffset: 220;
    transition: stroke-dashoffset 1s ease-out;
}

.progress-circle-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-text-primary);
}

/* ============================================
   Progress Bar
   ============================================ */

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-full);
    overflow: hidden;
    margin-top: var(--space-3);
}

.progress-bar-fill {
    height: 100%;
    background: var(--color-primary-gradient);
    border-radius: var(--radius-full);
    transition: width 0.6s ease-out;
}

/* ============================================
   Buttons
   ============================================ */

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-3) var(--space-5);
    font-family: var(--font-display);
    font-size: 0.875rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn-primary {
    background: var(--color-primary-gradient);
    color: white;
    box-shadow: 0 4px 14px rgba(46, 80, 144, 0.3);
}

.btn-primary:hover {
    transform: translateY(-1px);
    box-shadow: 0 6px 20px rgba(46, 80, 144, 0.4);
}

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

.btn-secondary {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.btn-secondary:hover {
    background: var(--color-border);
}

.btn-ghost {
    background: transparent;
    color: var(--color-text-secondary);
}

.btn-ghost:hover {
    background: var(--color-bg-tertiary);
    color: var(--color-text-primary);
}

.btn-sm {
    padding: var(--space-2) var(--space-3);
    font-size: 0.8125rem;
}

.btn-lg {
    padding: var(--space-4) var(--space-6);
    font-size: 1rem;
}

.btn-icon {
    width: 40px;
    height: 40px;
    padding: 0;
    border-radius: var(--radius-lg);
}

/* ============================================
   Form Elements
   ============================================ */

.form-group {
    margin-bottom: var(--space-4);
}

.form-label {
    display: block;
    font-family: var(--font-display);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: var(--space-2);
}

.form-input {
    width: 100%;
    padding: var(--space-3) var(--space-4);
    font-family: var(--font-body);
    font-size: 0.9375rem;
    color: var(--color-text-primary);
    background: var(--color-bg-tertiary);
    border: 2px solid transparent;
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast);
    outline: none;
}

.form-input:focus {
    border-color: var(--color-primary);
    background: var(--color-bg-elevated);
    box-shadow: 0 0 0 4px rgba(46, 80, 144, 0.1);
}

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

/* ============================================
   Lists
   ============================================ */

.list-item {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
    background: var(--color-bg-elevated);
    border-radius: var(--radius-lg);
    margin-bottom: var(--space-2);
    border: 1px solid var(--color-border-light);
    transition: all var(--transition-fast);
    cursor: pointer;
}

.list-item:hover {
    border-color: var(--color-border);
    box-shadow: var(--shadow-sm);
}

.list-item-icon {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.list-item-content {
    flex: 1;
    min-width: 0;
}

.list-item-title {
    font-family: var(--font-display);
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--color-text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.list-item-subtitle {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* ============================================
   Badges
   ============================================ */

.badge {
    display: inline-flex;
    align-items: center;
    padding: var(--space-1) var(--space-2);
    font-family: var(--font-display);
    font-size: 0.6875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.025em;
    border-radius: var(--radius-full);
}

.badge-primary {
    background: rgba(46, 80, 144, 0.1);
    color: var(--color-primary);
}

.badge-success {
    background: rgba(16, 185, 129, 0.1);
    color: var(--color-success);
}

.badge-warning {
    background: rgba(245, 158, 11, 0.1);
    color: var(--color-warning);
}

.badge-ghost {
    background: rgba(148, 163, 184, 0.1);
    color: var(--color-text-tertiary);
}

/* ============================================
   Streak Display
   ============================================ */

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

.streak-flame {
    font-size: 1.5rem;
    animation: flame-pulse 2s ease-in-out infinite;
}

@keyframes flame-pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.1); }
}

/* ============================================
   Quick Actions
   ============================================ */

.quick-actions {
    display: flex;
    gap: var(--space-2);
    flex-wrap: wrap;
}

.quick-action-btn {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-3);
    background: var(--color-bg-tertiary);
    border: none;
    border-radius: var(--radius-lg);
    font-family: var(--font-display);
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--color-text-primary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.quick-action-btn:hover {
    background: var(--color-border);
    transform: translateY(-1px);
}

.quick-action-btn svg {
    width: 16px;
    height: 16px;
    color: var(--color-primary);
}

/* ============================================
   AI Features Card
   ============================================ */

.ai-features-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-2);
    margin-top: var(--space-3);
}

.ai-feature-item {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-2);
    padding: var(--space-3);
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-lg);
    position: relative;
}

.ai-feature-icon {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg-elevated);
}

.ai-feature-icon svg {
    width: 20px;
    height: 20px;
    color: var(--color-primary);
}

.ai-feature-name {
    font-family: var(--font-display);
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.ai-feature-badge {
    position: absolute;
    top: var(--space-2);
    right: var(--space-2);
    font-size: 0.625rem;
    padding: 2px 6px;
    background: var(--color-accent-amber);
    color: white;
    border-radius: var(--radius-full);
    font-weight: 600;
}

/* ============================================
   Calendar Preview
   ============================================ */

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: var(--space-1);
    text-align: center;
}

.calendar-day-label {
    font-size: 0.625rem;
    font-weight: 600;
    color: var(--color-text-tertiary);
    text-transform: uppercase;
}

.calendar-day {
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    color: var(--color-text-secondary);
}

.calendar-day.today {
    background: var(--color-primary);
    color: white;
}

.calendar-day.has-event {
    position: relative;
}

.calendar-day.has-event::after {
    content: '';
    position: absolute;
    bottom: 2px;
    left: 50%;
    transform: translateX(-50%);
    width: 4px;
    height: 4px;
    background: var(--color-accent-rose);
    border-radius: var(--radius-full);
}

/* ============================================
   Modal
   ============================================ */

.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.6);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    z-index: 200;
    display: flex;
    align-items: flex-end;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal-content {
    background: var(--color-bg-elevated);
    border-radius: var(--radius-2xl) var(--radius-2xl) 0 0;
    width: 100%;
    max-width: 600px;
    max-height: 90vh;
    overflow-y: auto;
    transform: translateY(100%);
    transition: transform var(--transition-spring);
}

.modal-overlay.active .modal-content {
    transform: translateY(0);
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-4) var(--space-5);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    background: var(--color-bg-elevated);
    z-index: 1;
}

.modal-title {
    font-family: var(--font-display);
    font-size: 1.125rem;
    font-weight: 700;
}

.modal-close {
    width: 36px;
    height: 36px;
    border: none;
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background var(--transition-fast);
}

.modal-close:hover {
    background: var(--color-border);
}

.modal-body {
    padding: var(--space-4) var(--space-5);
}

/* ============================================
   Toast Notifications
   ============================================ */

.toast-container {
    position: fixed;
    top: var(--space-4);
    left: 50%;
    transform: translateX(-50%);
    z-index: 300;
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
    pointer-events: none;
}

.toast {
    background: var(--color-bg-elevated);
    color: var(--color-text-primary);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    font-family: var(--font-display);
    font-size: 0.875rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: var(--space-3);
    animation: toast-in 0.3s ease-out;
    pointer-events: auto;
    border: 1px solid var(--color-border);
}

.toast.success {
    border-left: 4px solid var(--color-success);
}

.toast.error {
    border-left: 4px solid var(--color-error);
}

.toast.warning {
    border-left: 4px solid var(--color-warning);
}

@keyframes toast-in {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================================
   Empty States
   ============================================ */

.empty-state {
    text-align: center;
    padding: var(--space-12) var(--space-6);
}

.empty-state-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--space-4);
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-2xl);
    display: flex;
    align-items: center;
    justify-content: center;
}

.empty-state-icon svg {
    width: 40px;
    height: 40px;
    color: var(--color-text-tertiary);
}

.empty-state-title {
    font-family: var(--font-display);
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--color-text-primary);
    margin-bottom: var(--space-2);
}

.empty-state-text {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    max-width: 280px;
    margin: 0 auto;
}

/* ============================================
   View Headers
   ============================================ */

.view-header {
    margin-bottom: var(--space-5);
}

.view-title {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--color-text-primary);
}

.view-subtitle {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    margin-top: var(--space-1);
}

/* ============================================
   Subject Cards
   ============================================ */

.subject-card {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4);
    background: var(--color-bg-elevated);
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-border-light);
    transition: all var(--transition-fast);
    cursor: pointer;
}

.subject-card:hover {
    border-color: var(--color-border);
    box-shadow: var(--shadow-md);
}

.subject-icon {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
}

.subject-info {
    flex: 1;
}

.subject-name {
    font-family: var(--font-display);
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.subject-meta {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin-top: 2px;
}

.subject-progress {
    width: 48px;
    text-align: right;
}

.subject-progress-value {
    font-family: var(--font-display);
    font-size: 0.875rem;
    font-weight: 700;
    color: var(--color-primary);
}

/* ============================================
   Flashcard Styles
   ============================================ */

.flashcard-container {
    perspective: 1000px;
    height: 280px;
}

.flashcard {
    position: relative;
    width: 100%;
    height: 100%;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
}

.flashcard.flipped {
    transform: rotateY(180deg);
}

.flashcard-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    background: var(--color-bg-elevated);
    border-radius: var(--radius-xl);
    padding: var(--space-6);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
}

.flashcard-back {
    transform: rotateY(180deg);
}

.flashcard-content {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-text-primary);
    line-height: 1.5;
}

.flashcard-hint {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    margin-top: var(--space-4);
}

/* ============================================
   Quiz Styles
   ============================================ */

.quiz-option {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-4);
    background: var(--color-bg-tertiary);
    border: 2px solid transparent;
    border-radius: var(--radius-lg);
    cursor: pointer;
    transition: all var(--transition-fast);
    margin-bottom: var(--space-2);
}

.quiz-option:hover {
    border-color: var(--color-border);
}

.quiz-option.selected {
    border-color: var(--color-primary);
    background: rgba(46, 80, 144, 0.05);
}

.quiz-option.correct {
    border-color: var(--color-success);
    background: rgba(16, 185, 129, 0.1);
}

.quiz-option.incorrect {
    border-color: var(--color-error);
    background: rgba(239, 68, 68, 0.1);
}

.quiz-option-letter {
    width: 32px;
    height: 32px;
    border-radius: var(--radius-full);
    background: var(--color-bg-elevated);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-display);
    font-size: 0.875rem;
    font-weight: 700;
    color: var(--color-text-secondary);
    flex-shrink: 0;
}

.quiz-option.selected .quiz-option-letter {
    background: var(--color-primary);
    color: white;
}

.quiz-option-text {
    font-size: 0.9375rem;
    color: var(--color-text-primary);
}

/* ============================================
   Planner Styles
   ============================================ */

.planner-day {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3);
    border-radius: var(--radius-lg);
    transition: background var(--transition-fast);
}

.planner-day:hover {
    background: var(--color-bg-tertiary);
}

.planner-day-date {
    width: 48px;
    text-align: center;
}

.planner-day-number {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-text-primary);
}

.planner-day-name {
    font-size: 0.75rem;
    color: var(--color-text-secondary);
    text-transform: uppercase;
}

.planner-day-tasks {
    flex: 1;
}

.planner-task {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.planner-task.completed {
    text-decoration: line-through;
    color: var(--color-text-tertiary);
}

/* ============================================
   Stats & Charts
   ============================================ */

.stats-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-3);
}

.stat-card {
    background: var(--color-bg-elevated);
    border-radius: var(--radius-xl);
    padding: var(--space-4);
    border: 1px solid var(--color-border-light);
}

.stat-value {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--color-text-primary);
}

.stat-label {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin-top: var(--space-1);
}

.stat-change {
    display: inline-flex;
    align-items: center;
    gap: 2px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-top: var(--space-2);
}

.stat-change.positive {
    color: var(--color-success);
}

.stat-change.negative {
    color: var(--color-error);
}

/* ============================================
   Achievement Badges
   ============================================ */

.badge-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-3);
}

.achievement-badge {
    text-align: center;
    padding: var(--space-3);
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-xl);
    transition: all var(--transition-fast);
}

.achievement-badge.unlocked {
    background: var(--color-bg-elevated);
    box-shadow: var(--shadow-sm);
}

.achievement-badge-icon {
    width: 56px;
    height: 56px;
    margin: 0 auto var(--space-2);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.75rem;
    background: var(--color-bg-elevated);
}

.achievement-badge.unlocked .achievement-badge-icon {
    background: var(--color-primary-gradient);
}

.achievement-badge-name {
    font-family: var(--font-display);
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.achievement-badge.locked .achievement-badge-icon {
    opacity: 0.4;
    filter: grayscale(1);
}

.achievement-badge.locked .achievement-badge-name {
    color: var(--color-text-tertiary);
}

/* ============================================
   Settings
   ============================================ */

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

.settings-section-title {
    font-family: var(--font-display);
    font-size: 0.8125rem;
    font-weight: 700;
    color: var(--color-text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--space-3);
    padding-left: var(--space-4);
}

.settings-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-4);
    background: var(--color-bg-elevated);
    border-bottom: 1px solid var(--color-border-light);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.settings-item:first-child {
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}

.settings-item:last-child {
    border-radius: 0 0 var(--radius-xl) var(--radius-xl);
    border-bottom: none;
}

.settings-item:only-child {
    border-radius: var(--radius-xl);
}

.settings-item:hover {
    background: var(--color-bg-tertiary);
}

.settings-item-left {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.settings-item-icon {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-md);
    background: var(--color-bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
}

.settings-item-icon svg {
    width: 18px;
    height: 18px;
    color: var(--color-primary);
}

.settings-item-content {
    display: flex;
    flex-direction: column;
}

.settings-item-title {
    font-family: var(--font-display);
    font-size: 0.9375rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.settings-item-subtitle {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
}

/* Toggle Switch */
.toggle {
    width: 48px;
    height: 28px;
    background: var(--color-bg-tertiary);
    border-radius: var(--radius-full);
    position: relative;
    cursor: pointer;
    transition: background var(--transition-fast);
}

.toggle.active {
    background: var(--color-primary);
}

.toggle-thumb {
    position: absolute;
    top: 2px;
    left: 2px;
    width: 24px;
    height: 24px;
    background: white;
    border-radius: var(--radius-full);
    transition: transform var(--transition-spring);
    box-shadow: var(--shadow-sm);
}

.toggle.active .toggle-thumb {
    transform: translateX(20px);
}

/* ============================================
   Responsive Design
   ============================================ */

@media (min-width: 640px) {
    .main-content {
        padding: var(--space-6);
    }
    
    .bento-grid {
        gap: var(--space-4);
    }
    
    .view-title {
        font-size: 1.75rem;
    }
}

@media (min-width: 768px) {
    .bento-grid {
        grid-template-columns: repeat(3, 1fr);
        max-width: 800px;
    }
    
    .bento-card.large,
    .bento-card.full-width {
        grid-column: span 3;
    }
    
    .bento-card.medium {
        grid-column: span 1;
    }
    
    .bento-card.small {
        grid-column: span 1;
    }
}

/* ============================================
   Animations
   ============================================ */

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.7;
    }
}

.animate-slide-up {
    animation: slideUp 0.4s ease-out;
}

.animate-scale-in {
    animation: scaleIn 0.3s ease-out;
}

/* Stagger animation delays */
.stagger-1 { animation-delay: 0.05s; }
.stagger-2 { animation-delay: 0.1s; }
.stagger-3 { animation-delay: 0.15s; }
.stagger-4 { animation-delay: 0.2s; }
.stagger-5 { animation-delay: 0.25s; }
.stagger-6 { animation-delay: 0.3s; }

/* ============================================
   Utility Classes
   ============================================ */

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }

.mt-2 { margin-top: var(--space-2); }
.mt-3 { margin-top: var(--space-3); }
.mt-4 { margin-top: var(--space-4); }

.mb-2 { margin-bottom: var(--space-2); }
.mb-3 { margin-bottom: var(--space-3); }
.mb-4 { margin-bottom: var(--space-4); }

.hidden { display: none !important; }
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
    background: var(--color-text-tertiary);
}