/* Study OS - Design System */
/* Indigo Ink palette adapted for academic focus */

@import url('https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&family=Inter:wght@400;500;600;700&display=swap');

:root {
  /* Core Colors - Indigo Ink Academic */
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-tertiary: #1a1a28;
  --bg-elevated: #222235;
  --bg-card: #1e1e2e;
  
  /* Accent Colors */
  --accent-primary: #7c3aed;
  --accent-secondary: #8b5cf6;
  --accent-tertiary: #a78bfa;
  --accent-glow: rgba(124, 58, 237, 0.3);
  
  /* Status Colors */
  --status-mastered: #10b981;
  --status-revision: #f59e0b;
  --status-weak: #ef4444;
  --status-learning: #3b82f6;
  --status-not-started: #6b7280;
  
  /* Text Colors */
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-tertiary: #64748b;
  --text-muted: #475569;
  
  /* Border & Shadow */
  --border-subtle: rgba(148, 163, 184, 0.08);
  --border-default: rgba(148, 163, 184, 0.12);
  --shadow-sm: 0 1px 2px 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, 0.5), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 40px var(--accent-glow);
  
  /* Typography */
  --font-display: 'Plus Jakarta Sans', sans-serif;
  --font-body: 'Inter', sans-serif;
  
  /* Spacing Scale */
  --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;
  --space-20: 5rem;
  --space-24: 6rem;
  
  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;
  
  /* Z-index Scale */
  --z-dropdown: 100;
  --z-sticky: 200;
  --z-modal: 300;
  --z-toast: 400;
}

/* Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

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

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

.text-display {
  font-family: var(--font-display);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.text-gradient {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-tertiary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Layout */
.app-container {
  display: flex;
  min-height: 100vh;
}

.main-content {
  flex: 1;
  margin-left: 280px;
  padding: var(--space-8);
  min-height: 100vh;
}

/* Sidebar */
.sidebar {
  position: fixed;
  left: 0;
  top: 0;
  width: 280px;
  height: 100vh;
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-subtle);
  display: flex;
  flex-direction: column;
  z-index: var(--z-sticky);
  padding: var(--space-6);
}

.sidebar-logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-8);
  padding-bottom: var(--space-6);
  border-bottom: 1px solid var(--border-subtle);
}

.logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

.logo-text {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.5rem;
  letter-spacing: -0.02em;
}

.logo-text span {
  color: var(--accent-secondary);
}

.sidebar-nav {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: all var(--transition-fast);
  cursor: pointer;
}

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

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

.nav-item i {
  width: 20px;
  text-align: center;
}

.nav-section {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-tertiary);
  margin: var(--space-6) 0 var(--space-3) 0;
  padding-left: var(--space-4);
}

.sidebar-footer {
  padding-top: var(--space-6);
  border-top: 1px solid var(--border-subtle);
}

.user-profile {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background var(--transition-fast);
}

.user-profile:hover {
  background: var(--bg-tertiary);
}

.user-avatar {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  font-size: 0.875rem;
}

.user-info {
  flex: 1;
}

.user-name {
  font-weight: 600;
  font-size: 0.875rem;
  color: var(--text-primary);
}

.user-class {
  font-size: 0.75rem;
  color: var(--text-tertiary);
}

/* Cards */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: all var(--transition-base);
}

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

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

.card-title {
  font-family: var(--font-display);
  font-size: 1.125rem;
  font-weight: 600;
}

.card-subtitle {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-top: var(--space-1);
}

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

.btn-primary {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  color: white;
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-glow);
}

.btn-secondary {
  background: var(--bg-elevated);
  color: var(--text-primary);
  border: 1px solid var(--border-default);
}

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

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

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

.btn-sm {
  padding: var(--space-2) var(--space-3);
  font-size: 0.75rem;
}

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

/* Progress Indicators */
.progress-ring {
  position: relative;
  width: 120px;
  height: 120px;
}

.progress-ring svg {
  transform: rotate(-90deg);
}

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

.progress-ring-fill {
  fill: none;
  stroke: url(#progressGradient);
  stroke-width: 8;
  stroke-linecap: round;
  transition: stroke-dashoffset var(--transition-slow);
}

.progress-text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-family: var(--font-display);
  font-size: 1.75rem;
  font-weight: 800;
}

.progress-label {
  text-align: center;
  margin-top: var(--space-2);
  font-size: 0.875rem;
  color: var(--text-secondary);
}

/* Status Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-full);
  font-size: 0.75rem;
  font-weight: 600;
}

.badge-mastered {
  background: rgba(16, 185, 129, 0.15);
  color: var(--status-mastered);
}

.badge-revision {
  background: rgba(245, 158, 11, 0.15);
  color: var(--status-revision);
}

.badge-weak {
  background: rgba(239, 68, 68, 0.15);
  color: var(--status-weak);
}

.badge-learning {
  background: rgba(59, 130, 246, 0.15);
  color: var(--status-learning);
}

.badge-not-started {
  background: rgba(107, 114, 128, 0.15);
  color: var(--text-tertiary);
}

/* Stats Grid */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-5);
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  display: flex;
  align-items: center;
  gap: var(--space-4);
  transition: all var(--transition-base);
}

.stat-card:hover {
  border-color: var(--border-default);
  transform: translateY(-2px);
}

.stat-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

.stat-icon.purple { background: rgba(124, 58, 237, 0.15); color: var(--accent-secondary); }
.stat-icon.green { background: rgba(16, 185, 129, 0.15); color: var(--status-mastered); }
.stat-icon.orange { background: rgba(245, 158, 11, 0.15); color: var(--status-revision); }
.stat-icon.red { background: rgba(239, 68, 68, 0.15); color: var(--status-weak); }
.stat-icon.blue { background: rgba(59, 130, 246, 0.15); color: var(--status-learning); }

.stat-content {
  flex: 1;
}

.stat-value {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.stat-label {
  font-size: 0.875rem;
  color: var(--text-secondary);
}

/* Tables */
.data-table {
  width: 100%;
  border-collapse: collapse;
}

.data-table th {
  text-align: left;
  padding: var(--space-3) var(--space-4);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-tertiary);
  border-bottom: 1px solid var(--border-subtle);
}

.data-table td {
  padding: var(--space-4);
  border-bottom: 1px solid var(--border-subtle);
  font-size: 0.875rem;
}

.data-table tr:hover td {
  background: var(--bg-tertiary);
}

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

.form-label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: var(--space-2);
}

.form-input {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  background: var(--bg-tertiary);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 0.875rem;
  transition: all var(--transition-fast);
}

.form-input:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-glow);
}

.form-select {
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right var(--space-3) center;
  padding-right: var(--space-10);
}

/* Onboarding */
.onboarding-container {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-8);
  background: radial-gradient(ellipse at top, var(--bg-secondary), var(--bg-primary));
}

.onboarding-card {
  width: 100%;
  max-width: 560px;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-10);
}

.onboarding-header {
  text-align: center;
  margin-bottom: var(--space-8);
}

.onboarding-title {
  font-size: 1.75rem;
  margin-bottom: var(--space-2);
}

.onboarding-subtitle {
  color: var(--text-secondary);
}

.step-indicator {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  margin-bottom: var(--space-8);
}

.step-dot {
  width: 8px;
  height: 8px;
  border-radius: var(--radius-full);
  background: var(--bg-elevated);
  transition: all var(--transition-base);
}

.step-dot.active {
  background: var(--accent-primary);
  width: 24px;
}

.step-dot.completed {
  background: var(--accent-secondary);
}

/* Subject Cards */
.subject-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: var(--space-5);
}

.subject-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  cursor: pointer;
  transition: all var(--transition-base);
}

.subject-card:hover {
  border-color: var(--accent-primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

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

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

.subject-progress {
  margin-top: var(--space-4);
}

.progress-bar {
  height: 6px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-bottom: var(--space-2);
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-primary), var(--accent-secondary));
  border-radius: var(--radius-full);
  transition: width var(--transition-slow);
}

.progress-stats {
  display: flex;
  justify-content: space-between;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

/* Daily Plan */
.daily-plan {
  background: linear-gradient(135deg, var(--bg-card), var(--bg-secondary));
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
}

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

.plan-title {
  font-size: 1.5rem;
}

.plan-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-4);
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-3);
  transition: all var(--transition-fast);
}

.plan-item:hover {
  background: var(--bg-elevated);
}

.plan-number {
  width: 32px;
  height: 32px;
  background: var(--accent-primary);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.875rem;
  flex-shrink: 0;
}

.plan-content {
  flex: 1;
}

.plan-task {
  font-weight: 600;
  margin-bottom: var(--space-1);
}

.plan-meta {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.plan-duration {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.plan-reason {
  color: var(--accent-tertiary);
}

/* Timer */
.timer-container {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-5);
  box-shadow: var(--shadow-lg);
  z-index: var(--z-sticky);
  min-width: 280px;
}

.timer-display {
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 700;
  text-align: center;
  margin-bottom: var(--space-4);
  font-variant-numeric: tabular-nums;
}

.timer-controls {
  display: flex;
  gap: var(--space-2);
}

.timer-btn {
  flex: 1;
  padding: var(--space-2);
  border-radius: var(--radius-md);
  border: none;
  background: var(--bg-tertiary);
  color: var(--text-primary);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.timer-btn:hover {
  background: var(--accent-primary);
}

/* Mobile Navigation */
.mobile-nav {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--bg-card);
  border-top: 1px solid var(--border-subtle);
  padding: var(--space-2) var(--space-4);
  z-index: var(--z-sticky);
}

.mobile-nav-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2);
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.75rem;
  flex: 1;
}

.mobile-nav-item.active {
  color: var(--accent-secondary);
}

.mobile-nav-item i {
  font-size: 1.25rem;
}

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

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

@keyframes slideIn {
  from { transform: translateX(-100%); }
  to { transform: translateX(0); }
}

.animate-fade-in {
  animation: fadeIn 0.4s ease forwards;
}

.animate-pulse {
  animation: pulse 2s ease infinite;
}

/* Streak */
.streak-display {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-display);
  font-weight: 700;
  color: var(--status-revision);
}

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

/* Empty States */
.empty-state {
  text-align: center;
  padding: var(--space-16);
}

.empty-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto var(--space-6);
  background: var(--bg-tertiary);
  border-radius: var(--radius-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
}

.empty-title {
  font-size: 1.25rem;
  margin-bottom: var(--space-2);
}

.empty-text {
  color: var(--text-secondary);
  margin-bottom: var(--space-6);
}

/* Responsive */
@media (max-width: 1024px) {
  .sidebar {
    transform: translateX(-100%);
    transition: transform var(--transition-base);
  }
  
  .sidebar.open {
    transform: translateX(0);
  }
  
  .main-content {
    margin-left: 0;
  }
  
  .mobile-nav {
    display: flex;
    justify-content: space-around;
  }
  
  .main-content {
    padding-bottom: 80px;
  }
}

@media (max-width: 768px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }
  
  .subject-grid {
    grid-template-columns: 1fr;
  }
  
  .onboarding-card {
    padding: var(--space-6);
  }
  
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.5rem; }
}

/* Scrollbar */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

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

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

/* Utility Classes */
.text-center { text-align: center; }
.text-right { text-align: right; }
.font-medium { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }

.mt-1 { margin-top: var(--space-1); }
.mt-2 { margin-top: var(--space-2); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-2 { margin-bottom: var(--space-2); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }

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

.hidden { display: none; }