/* ==========================================================
   TechTeach.lk — Main Stylesheet
   ========================================================== */

:root {
  --primary: #800080;
  --primary-dark: #800080;
  --primary-light: #800080;
  --secondary: #06b6d4;
  --accent: #f59e0b;
  --success: #10b981;
  --danger: #ef4444;

  --dark: #0b1120;
  --dark-2: #0f172a;
  --dark-3: #1e293b;

  --text-light: #f1f5f9;
  --text-muted: #94a3b8;

  --glass-bg: rgba(255, 255, 255, 0.06);
  --glass-border: rgba(255, 255, 255, 0.12);
  --glass-blur: blur(16px);

  --radius-sm: 10px;
  --radius-md: 16px;
  --radius-lg: 24px;

  --shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.25);
  --shadow-md: 0 10px 30px rgba(0, 0, 0, 0.35);
  --shadow-glow: 0 0 40px rgba(79, 70, 229, 0.35);

  --transition: all 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Segoe UI', system-ui, -apple-system, Roboto, sans-serif;
  background:
    radial-gradient(circle at 15% 10%, rgba(79, 70, 229, 0.25), transparent 40%),
    radial-gradient(circle at 85% 90%, rgba(6, 182, 212, 0.2), transparent 45%),
    linear-gradient(160deg, var(--dark) 0%, var(--dark-2) 55%, var(--dark-3) 100%);
  background-attachment: fixed;
  color: var(--text-light);
  min-height: 100vh;
  line-height: 1.6;
}

a { text-decoration: none; color: inherit; }
ul { list-style: none; }
img { max-width: 100%; display: block; }
button { font-family: inherit; cursor: pointer; border: none; }

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------------- Scrollbar ---------------- */
::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-track { background: var(--dark-2); }
::-webkit-scrollbar-thumb {
  background: linear-gradient(var(--primary), var(--secondary));
  border-radius: 10px;
}

/* ---------------- Glass helper ---------------- */
.glass {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}

/* ================= NAVBAR ================= */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(11, 17, 32, 0.7);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--glass-border);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 16px;
  padding-bottom: 16px;
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: 0.5px;
  background: linear-gradient(90deg, var(--primary-light), var(--secondary));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

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

.nav-links {
  display: flex;
  gap: 10px;
  align-items: center;
}

.nav-btn {
  padding: 10px 20px;
  border-radius: 999px;
  color: var(--text-light);
  font-weight: 600;
  font-size: 0.95rem;
  transition: var(--transition);
  border: 1px solid transparent;
}

.nav-btn:hover {
  background: rgba(255, 255, 255, 0.08);
  border-color: var(--glass-border);
}

.nav-btn.active {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  box-shadow: var(--shadow-glow);
}

/* ================= HERO ================= */
.hero {
  padding: 100px 0 70px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: -20%;
  background: radial-gradient(circle at 50% 20%, rgba(79, 70, 229, 0.25), transparent 60%);
  pointer-events: none;
  z-index: -1;
}

.hero-badge {
  display: inline-block;
  padding: 8px 18px;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--secondary);
  margin-bottom: 22px;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.4rem);
  font-weight: 800;
  line-height: 1.15;
  max-width: 900px;
  margin: 0 auto 20px;
  background: linear-gradient(100deg, #ffffff, var(--primary-light) 60%, var(--secondary));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero p {
  font-size: clamp(1rem, 2vw, 1.2rem);
  color: var(--text-muted);
  max-width: 620px;
  margin: 0 auto 36px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 34px;
  border-radius: 999px;
  font-weight: 700;
  font-size: 1rem;
  transition: var(--transition);
  cursor: pointer;
}

.btn-primary {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  color: #fff;
  box-shadow: var(--shadow-glow);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 0 55px rgba(79, 70, 229, 0.5);
}

.btn-outline {
  background: transparent;
  color: var(--text-light);
  border: 1px solid var(--glass-border);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.08);
  border-color: var(--primary-light);
}

.btn-secondary {
  background: var(--dark-3);
  color: var(--text-light);
  border: 1px solid var(--glass-border);
}
.btn-secondary:hover { background: #263349; }

.btn-danger {
  background: rgba(239, 68, 68, 0.15);
  color: #fca5a5;
  border: 1px solid rgba(239, 68, 68, 0.4);
}
.btn-danger:hover { background: rgba(239, 68, 68, 0.3); }

.btn-sm { padding: 8px 16px; font-size: 0.85rem; }
.btn:disabled { opacity: 0.4; cursor: not-allowed; transform: none !important; }

/* ================= SECTION HEADINGS ================= */
.section {
  padding: 60px 0;
}

.section-head {
  text-align: center;
  margin-bottom: 46px;
}

.section-head h2 {
  font-size: clamp(1.6rem, 3vw, 2.3rem);
  font-weight: 800;
  margin-bottom: 12px;
}

.section-head p {
  color: var(--text-muted);
  max-width: 560px;
  margin: 0 auto;
}

/* ================= SUBJECT CARDS ================= */
.subject-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.subject-card {
  padding: 40px 28px;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  position: relative;
  overflow: hidden;
}

.subject-card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(79, 70, 229, 0.15), rgba(6, 182, 212, 0.1));
  opacity: 0;
  transition: var(--transition);
}

.subject-card:hover {
  transform: translateY(-8px);
  border-color: var(--primary-light);
  box-shadow: var(--shadow-glow);
}

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

.subject-icon {
  font-size: 3rem;
  margin-bottom: 18px;
  position: relative;
}

.subject-card h3 {
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: 6px;
  position: relative;
}

.subject-card h4 {
  font-size: 1rem;
  color: var(--secondary);
  font-weight: 600;
  margin-bottom: 12px;
  position: relative;
}

.subject-card p {
  color: var(--text-muted);
  font-size: 0.92rem;
  position: relative;
}

/* ================= FOOTER ================= */
.footer {
  border-top: 1px solid var(--glass-border);
  padding: 40px 0;
  margin-top: 40px;
}

.footer .container {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.footer p { color: var(--text-muted); font-size: 0.9rem; }

.social-links { display: flex; gap: 14px; }

.social-links a {
  width: 38px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  transition: var(--transition);
  font-size: 1rem;
}

.social-links a:hover {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  transform: translateY(-3px);
}

/* ================= DASHBOARD ================= */
.dashboard-header {
  text-align: center;
  padding: 60px 0 20px;
}

.dashboard-header h1 { font-size: clamp(1.6rem, 3vw, 2.2rem); font-weight: 800; }
.dashboard-header p { color: var(--text-muted); margin-top: 10px; }

.selector-panel {
  padding: 32px;
  margin: 30px auto 50px;
  max-width: 900px;
}

.selector-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-bottom: 28px;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 10px;
}

select, input, textarea {
  width: 100%;
  padding: 13px 16px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--glass-border);
  color: var(--text-light);
  font-size: 0.95rem;
  transition: var(--transition);
}

select:focus, input:focus, textarea:focus {
  outline: none;
  border-color: var(--primary-light);
  background: rgba(255, 255, 255, 0.08);
}

select:disabled { opacity: 0.5; }

select option { background: var(--dark-2); color: var(--text-light); }

.topic-info-box {
  padding: 22px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--glass-border);
  margin-bottom: 26px;
  min-height: 60px;
}

.topic-info-box h3 { font-size: 1.1rem; margin-bottom: 8px; }
.topic-info-box p { color: var(--text-muted); font-size: 0.9rem; }

.action-buttons {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.action-buttons .btn { flex: 1; justify-content: center; min-width: 200px; }

.empty-state {
  text-align: center;
  color: var(--text-muted);
  padding: 30px 0;
}

/* ================= VIDEO PAGE ================= */
.video-page-wrap {
  padding: 40px 0 80px;
  max-width: 960px;
  margin: 0 auto;
}

.breadcrumb-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
  flex-wrap: wrap;
  gap: 12px;
}

.video-frame-wrap {
  position: relative;
  width: 100%;
  padding-top: 56.25%;
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-md);
  background: #000;
  margin-bottom: 26px;
}

.video-frame-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.video-meta { padding: 28px; margin-bottom: 26px; }
.video-meta h1 { font-size: 1.6rem; margin-bottom: 10px; }
.video-meta p { color: var(--text-muted); }

.video-nav-buttons {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

/* ================= ADMIN ================= */
.admin-lock {
  min-height: 80vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.admin-lock-card {
  padding: 48px 40px;
  max-width: 400px;
  width: 100%;
  text-align: center;
}

.admin-lock-card h2 { margin-bottom: 8px; font-size: 1.5rem; }
.admin-lock-card p { color: var(--text-muted); margin-bottom: 26px; font-size: 0.9rem; }
.admin-lock-card .form-group { margin-bottom: 18px; text-align: left; }
.admin-lock-card .btn { width: 100%; justify-content: center; margin-top: 6px; }
.error-msg { color: #fca5a5; font-size: 0.85rem; margin-top: 10px; min-height: 18px; }

.admin-topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 30px 0 10px;
  flex-wrap: wrap;
  gap: 12px;
}

.admin-topbar h1 { font-size: 1.6rem; font-weight: 800; }

.admin-subject-tabs {
  display: flex;
  gap: 12px;
  margin: 24px 0 36px;
  flex-wrap: wrap;
}

.admin-tab {
  padding: 12px 26px;
  border-radius: 999px;
  font-weight: 700;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  transition: var(--transition);
}

.admin-tab:hover { border-color: var(--primary-light); }

.admin-tab.active {
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-color: transparent;
  box-shadow: var(--shadow-glow);
}

.admin-columns {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
  align-items: start;
}

.admin-panel-box { padding: 26px; }

.panel-title-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.panel-title-row h3 { font-size: 1.15rem; font-weight: 700; }

.list-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding: 16px;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid var(--glass-border);
  margin-bottom: 12px;
  transition: var(--transition);
}

.list-item:hover { border-color: var(--primary-light); }
.list-item.selected { border-color: var(--secondary); background: rgba(6, 182, 212, 0.1); }

.list-item-main { flex: 1; cursor: pointer; }
.list-item-main h4 { font-size: 0.98rem; margin-bottom: 4px; }
.list-item-main span { font-size: 0.8rem; color: var(--text-muted); }

.list-item-actions { display: flex; gap: 8px; flex-shrink: 0; }

.icon-btn {
  width: 34px;
  height: 34px;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--glass-border);
  transition: var(--transition);
  font-size: 0.9rem;
}

.icon-btn:hover { background: rgba(255, 255, 255, 0.14); }
.icon-btn.danger:hover { background: rgba(239, 68, 68, 0.25); }

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(3, 6, 15, 0.7);
  backdrop-filter: blur(6px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
}

.modal-overlay.open { display: flex; }

.modal-box {
  width: 100%;
  max-width: 480px;
  padding: 32px;
  max-height: 90vh;
  overflow-y: auto;
}

.modal-box h3 { margin-bottom: 22px; font-size: 1.2rem; }
.modal-box .form-group { margin-bottom: 16px; }
.modal-actions { display: flex; gap: 12px; margin-top: 22px; }
.modal-actions .btn { flex: 1; justify-content: center; }

.toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  padding: 14px 22px;
  border-radius: var(--radius-sm);
  background: var(--dark-3);
  border: 1px solid var(--glass-border);
  box-shadow: var(--shadow-md);
  z-index: 2000;
  font-size: 0.9rem;
  font-weight: 600;
  transform: translateY(120%);
  transition: transform 0.3s ease;
}

.toast.show { transform: translateY(0); }
.toast.success { border-color: var(--success); color: #86efac; }
.toast.error { border-color: var(--danger); color: #fca5a5; }

/* ================= RESPONSIVE ================= */
@media (max-width: 900px) {
  .subject-grid { grid-template-columns: 1fr 1fr; }
  .selector-grid { grid-template-columns: 1fr; }
  .admin-columns { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
  .subject-grid { grid-template-columns: 1fr; }
  .nav-links { gap: 4px; }
  .nav-btn { padding: 8px 14px; font-size: 0.85rem; }
  .hero { padding: 70px 0 50px; }
  .action-buttons .btn { min-width: 100%; }
  .footer .container { flex-direction: column; text-align: center; }
  .admin-topbar { flex-direction: column; align-items: flex-start; }
  .video-nav-buttons { flex-direction: column; }
  .video-nav-buttons .btn { width: 100%; justify-content: center; }
}