/* Modern CSS Reset and Base Styles */
:root {
  /* Color Variables */
  --primary: #2563eb;
  --primary-dark: #1e3a8a;
  --success: #22c55e;
  --warning: #f59e42;
  --danger: #ef4444;
  --light: #f7f8fa;
  --dark: #1e293b;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --border-color: #e2e8f0;
  
  /* Subject Colors */
  --color-math: #f87171;
  --color-biology: #34d399;
  --color-chemistry: #fbbf24;
  --color-literature: #a78bfa;
  --color-physics: #60a5fa;
  --color-english: #f472b6;
  --color-economics: #38bdf8;
  --color-accounting: #f59e42;
  --color-government: #6366f1;
  --color-commerce: #10b981;

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 2.5rem;

  /* Border Radius */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
}

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

body {
  font-family: 'Inter', sans-serif;
  background: var(--light);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* Layout Components */
.layout {
  display: flex;
  min-height: 100vh;
}

/* Modernized Sidebar */
.sidebar {
  width: 280px;
  background: var(--dark);
  color: #fff;
  padding: var(--spacing-lg) var(--spacing-md);
  position: fixed;
  height: 100vh;
  transition: transform 0.3s ease;
  z-index: 100;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.sidebar__logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: 1.5rem;
  font-weight: 700;
  color: #fff;
  margin-bottom: var(--spacing-xl);
  text-decoration: none;
  transition: opacity 0.2s;
}

.sidebar__logo:hover {
  opacity: 0.9;
}

.sidebar__menu {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
  overflow-y: auto;
  flex: 1;
  padding-right: var(--spacing-sm);
  margin-right: calc(var(--spacing-sm) * -1);
}

.sidebar__menu::-webkit-scrollbar {
  width: 4px;
}

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

.sidebar__menu::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.2);
  border-radius: 4px;
}

.sidebar__item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: var(--spacing-sm) var(--spacing-md);
  color: #fff;
  text-decoration: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  transition: all 0.2s;
}

.sidebar__item:hover, .sidebar__item.active {
  background: rgba(255, 255, 255, 0.1);
  color: var(--primary);
  transform: translateX(4px);
}

/* Main Content Area */
.main-content {
  flex: 1;
  padding: var(--spacing-xl);
  margin-left: 280px;
  min-height: 100vh;
  transition: margin-left 0.3s ease;
}

/* Modern Components */
.card {
  background: #fff;
  border-radius: var(--radius-lg);
  box-shadow: 0 2px 8px rgba(30,41,59,0.07);
  padding: var(--spacing-lg);
  transition: box-shadow 0.3s, transform 0.3s;
}

.card:hover {
  box-shadow: 0 4px 20px rgba(30,41,59,0.1);
  transform: translateY(-2px);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.625rem 1.25rem;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.95rem;
  border: none;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--primary);
  color: var(--primary);
}

.btn-outline:hover {
  background: var(--primary);
  color: #fff;
}

.btn-full {
  width: 100%;
}

.hidden {
  /* keep utility hidden behavior but avoid !important so responsive utilities can override it */
  display: none;
}

/* Navigation Component */
.nav {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.nav-link {
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-link:hover {
  color: var(--primary);
}

/* Page Header Components */
.page-header {
  margin-bottom: var(--spacing-xl);
}

.page-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--spacing-sm);
}

.page-description {
  color: var(--text-secondary);
  font-size: 1.1rem;
}

/* Badge Components */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.35rem 0.75rem;
  border-radius: 9999px;
  font-size: 0.875rem;
  font-weight: 500;
}

.badge-primary { background: rgba(37,99,235,0.1); color: var(--primary); }
.badge-success { background: rgba(34,197,94,0.1); color: var(--success); }
.badge-warning { background: rgba(245,158,66,0.1); color: var(--warning); }
.badge-danger { background: rgba(239,68,68,0.1); color: var(--danger); }

/* Avatar Components */
.avatar {
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 50%;
  object-fit: cover;
}

.avatar-sm { width: 2rem; height: 2rem; }
.avatar-lg { width: 3rem; height: 3rem; }
.avatar-xl { width: 4rem; height: 4rem; }

/* Utility Classes */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.gap-1 { gap: var(--spacing-xs); }
.gap-2 { gap: var(--spacing-sm); }
.gap-3 { gap: var(--spacing-md); }
.gap-4 { gap: var(--spacing-lg); }

/* Status Indicators */
.status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
}

.status-dot.active { background: var(--success); }
.status-dot.inactive { background: var(--text-secondary); }
.status-dot.busy { background: var(--warning); }
.status-dot.offline { background: var(--danger); }

/* Form Elements */
.input {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  transition: all 0.2s;
}

.input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

/* Search Bar */
.search-bar {
  position: relative;
  max-width: 400px;
}

.search-input {
  width: 100%;
  padding: 0.75rem 1rem 0.75rem 2.5rem;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  font-size: 1rem;
  background: #fff;
  transition: all 0.2s;
}

.search-input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

/* Subject Cards */
.subject-card {
  background: #fff;
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  text-align: center;
  font-weight: 600;
  font-size: 1.1rem;
  color: #fff;
  cursor: pointer;
  transition: all 0.3s;
  min-width: 180px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-sm);
}

.subject-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 20px rgba(0,0,0,0.15);
}

/* Subject Colors */
.subject-card.math { background: var(--color-math); }
.subject-card.biology { background: var(--color-biology); }
.subject-card.chemistry { background: var(--color-chemistry); }
.subject-card.literature { background: var(--color-literature); }
.subject-card.physics { background: var(--color-physics); }
.subject-card.english { background: var(--color-english); }
.subject-card.economics { background: var(--color-economics); }
.subject-card.accounting { background: var(--color-accounting); }
.subject-card.government { background: var(--color-government); }
.subject-card.commerce { background: var(--color-commerce); }

/* Grid Layouts */
.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

/* Responsive Design */
@media (max-width: 1024px) {
  .sidebar {
    width: 240px;
  }
  .main-content {
    margin-left: 240px;
  }
  .grid-4 { grid-template-columns: repeat(3, 1fr); }
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
  }
  .sidebar.active {
    transform: translateX(0);
  }
  .main-content {
    margin-left: 0;
    padding: var(--spacing-md);
  }
  .grid-3, .grid-4 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 480px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
}