/* TechVision Portal - Dashboard UI */
:root {
  --sidebar-bg: #1a1d2e;
  --sidebar-hover: #252a40;
  --sidebar-active: #2d3555;
  --sidebar-text: #a0a8c0;
  --sidebar-text-active: #ffffff;
  --page-bg: #f5f3ef;
  --card-bg: #ffffff;
  --primary: #0d9488;
  --primary-hover: #0f766e;
  --primary-light: #ccfbf1;
  --accent: #7c3aed;
  --accent-light: #ede9fe;
  --success: #059669;
  --success-bg: #d1fae5;
  --warning: #d97706;
  --warning-bg: #fef3c7;
  --danger: #dc2626;
  --danger-bg: #fee2e2;
  --info: #2563eb;
  --info-bg: #dbeafe;
  --text: #1e293b;
  --text-muted: #64748b;
  --border: #e2e8f0;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,.08), 0 1px 2px rgba(0,0,0,.04);
  --shadow-md: 0 4px 12px rgba(0,0,0,.08);
  --sidebar-width: 260px;
  --font: 'Inter', system-ui, -apple-system, sans-serif;
}

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

body {
  font-family: var(--font);
  background: var(--page-bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

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

.sidebar {
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  color: var(--sidebar-text);
  position: fixed;
  top: 0; left: 0; bottom: 0;
  z-index: 100;
  display: flex;
  flex-direction: column;
  transition: transform .25s ease;
}

.sidebar-brand {
  padding: 1.25rem 1.5rem;
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
  border-bottom: 1px solid rgba(255,255,255,.08);
  display: flex;
  align-items: center;
  gap: .5rem;
}

.sidebar-brand span { color: var(--primary); }

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 0;
}

.sidebar-nav a {
  display: flex;
  align-items: center;
  gap: .75rem;
  padding: .7rem 1.5rem;
  color: var(--sidebar-text);
  text-decoration: none;
  font-size: .9rem;
  transition: background .15s, color .15s;
}

.sidebar-nav a:hover { background: var(--sidebar-hover); color: #fff; }
.sidebar-nav a.active { background: var(--sidebar-active); color: var(--sidebar-text-active); border-left: 3px solid var(--primary); }

.sidebar-nav .nav-icon { width: 20px; text-align: center; opacity: .8; }

.main-content {
  margin-left: var(--sidebar-width);
  flex: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.topbar {
  background: var(--card-bg);
  padding: .85rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 50;
}

.topbar h1 { font-size: 1.15rem; font-weight: 600; }

.topbar-right { display: flex; align-items: center; gap: 1rem; }

.page-body { padding: 1.5rem; flex: 1; }

/* Cards */
.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.25rem;
  margin-bottom: 1.25rem;
}

.card-title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.stat-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.25rem;
  text-align: center;
}

.stat-card .stat-value { font-size: 1.75rem; font-weight: 700; color: var(--text); }
.stat-card .stat-label { font-size: .8rem; color: var(--text-muted); margin-top: .25rem; }
.stat-card.teal .stat-value { color: var(--primary); }
.stat-card.purple .stat-value { color: var(--accent); }
.stat-card.green .stat-value { color: var(--success); }
.stat-card.orange .stat-value { color: var(--warning); }
.stat-card.red .stat-value { color: var(--danger); }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: .4rem;
  padding: .55rem 1.1rem;
  border-radius: var(--radius-sm);
  font-size: .875rem;
  font-weight: 500;
  border: none;
  cursor: pointer;
  transition: background .15s, transform .1s;
  text-decoration: none;
  line-height: 1.4;
}

.btn:active { transform: scale(.98); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-hover); color: #fff; text-decoration: none; }
.btn-accent { background: var(--accent); color: #fff; }
.btn-accent:hover { background: #6d28d9; color: #fff; text-decoration: none; }
.btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn-outline:hover { background: var(--page-bg); text-decoration: none; }
.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { background: #b91c1c; }
.btn-success { background: var(--success); color: #fff; }
.btn-sm { padding: .35rem .75rem; font-size: .8rem; }
.btn-block { width: 100%; justify-content: center; }
.btn:disabled { opacity: .5; cursor: not-allowed; }

/* Forms */
.form-group { margin-bottom: 1rem; }
.form-group label { display: block; font-size: .85rem; font-weight: 500; margin-bottom: .35rem; color: var(--text); }
.form-control {
  width: 100%;
  padding: .6rem .85rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: .9rem;
  font-family: inherit;
  background: #fff;
  transition: border-color .15s;
}
.form-control:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-light); }
textarea.form-control { min-height: 100px; resize: vertical; }
select.form-control { appearance: auto; }

/* Tables */
.table-wrap { overflow-x: auto; }
table.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: .875rem;
}
table.data-table th {
  text-align: left;
  padding: .75rem 1rem;
  background: var(--page-bg);
  font-weight: 600;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}
table.data-table td {
  padding: .75rem 1rem;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
}
table.data-table tr:hover td { background: #fafaf9; }

/* Badges */
.badge {
  display: inline-block;
  padding: .2rem .6rem;
  border-radius: 999px;
  font-size: .75rem;
  font-weight: 600;
  letter-spacing: .02em;
}
.badge-success { background: var(--success-bg); color: var(--success); }
.badge-warning { background: var(--warning-bg); color: var(--warning); }
.badge-danger { background: var(--danger-bg); color: var(--danger); }
.badge-info { background: var(--info-bg); color: var(--info); }
.badge-purple { background: var(--accent-light); color: var(--accent); }
.badge-muted { background: #f1f5f9; color: var(--text-muted); }

/* Alerts */
.alert {
  padding: .85rem 1.15rem;
  border-radius: var(--radius-sm);
  margin-bottom: 1rem;
  font-size: .9rem;
}
.alert-success { background: var(--success-bg); color: var(--success); border: 1px solid #a7f3d0; }
.alert-error { background: var(--danger-bg); color: var(--danger); border: 1px solid #fecaca; }
.alert-info { background: var(--info-bg); color: var(--info); border: 1px solid #bfdbfe; }

/* Empty state */
.empty-state {
  text-align: center;
  padding: 2.5rem 1rem;
  color: var(--text-muted);
}
.empty-state .empty-icon { font-size: 2.5rem; margin-bottom: .75rem; opacity: .5; }

/* Login */
.login-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #1a1d2e 0%, #2d3555 100%);
  padding: 1rem;
}
.login-card {
  background: #fff;
  border-radius: 16px;
  padding: 2.5rem;
  width: 100%;
  max-width: 400px;
  box-shadow: var(--shadow-md);
}
.login-card h1 { text-align: center; margin-bottom: .25rem; font-size: 1.5rem; }
.login-card .subtitle { text-align: center; color: var(--text-muted); margin-bottom: 1.75rem; font-size: .9rem; }

/* Assignment card */
.assignment-card {
  background: linear-gradient(135deg, #f0fdfa 0%, #fff 100%);
  border: 1px solid #99f6e4;
  border-radius: var(--radius);
  padding: 1.5rem;
}
.assignment-email {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--primary);
  word-break: break-all;
  margin: .75rem 0;
}
.assignment-meta { display: flex; gap: 1rem; flex-wrap: wrap; margin-bottom: 1rem; }

/* Mobile */
.mobile-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text);
  padding: .25rem;
}

@media (max-width: 900px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); }
  .main-content { margin-left: 0; }
  .mobile-toggle { display: block; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 500px) {
  .stats-grid { grid-template-columns: 1fr; }
  .page-body { padding: 1rem; }
  .assignment-meta { flex-direction: column; gap: .5rem; }
}

/* Overlay for mobile sidebar */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.4);
  z-index: 99;
}
.sidebar-overlay.show { display: block; }

/* Toggle switch */
.toggle {
  position: relative;
  width: 48px;
  height: 26px;
  display: inline-block;
}
.toggle input { opacity: 0; width: 0; height: 0; }
.toggle .slider {
  position: absolute;
  cursor: pointer;
  inset: 0;
  background: #cbd5e1;
  border-radius: 26px;
  transition: .2s;
}
.toggle .slider::before {
  content: '';
  position: absolute;
  height: 20px; width: 20px;
  left: 3px; bottom: 3px;
  background: #fff;
  border-radius: 50%;
  transition: .2s;
}
.toggle input:checked + .slider { background: var(--primary); }
.toggle input:checked + .slider::before { transform: translateX(22px); }

/* Flex helpers */
.flex { display: flex; }
.flex-between { display: flex; justify-content: space-between; align-items: center; }
.gap-1 { gap: .5rem; }
.gap-2 { gap: 1rem; }
.mt-1 { margin-top: .5rem; }
.mt-2 { margin-top: 1rem; }
.mb-1 { margin-bottom: .5rem; }
.mb-2 { margin-bottom: 1rem; }
.text-muted { color: var(--text-muted); }
.text-sm { font-size: .85rem; }
.fw-600 { font-weight: 600; }