:root {
  --primary: #4f46e5;
  --primary-dark: #4338ca;
  --text: #1f2430;
  --muted: #6b7280;
  --border: #e5e7eb;
  --bg: #f8f9fb;
  --card: #ffffff;
  --radius: 10px;
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
.container { max-width: 1100px; margin: 0 auto; padding: 0 20px; }
.muted { color: var(--muted); }

/* Header */
.site-header { background: var(--card); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 10; }
.header-inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.brand { display: flex; align-items: center; gap: 8px; font-weight: 700; font-size: 19px; color: var(--text); }
.brand:hover { text-decoration: none; }
.brand-logo { height: 32px; width: auto; }
.main-nav { display: flex; align-items: center; gap: 20px; }
.main-nav a { color: var(--text); font-weight: 500; }
.main-nav a:hover { color: var(--primary); text-decoration: none; }
.btn-nav { background: var(--primary); color: #fff !important; padding: 8px 16px; border-radius: 8px; }

/* Layout */
.page-content { padding: 30px 20px 60px; min-height: 60vh; }

/* Alerts */
.alert { padding: 12px 16px; border-radius: var(--radius); margin-bottom: 18px; font-size: 14px; }
.alert-success { background: #dcfce7; color: #166534; }
.alert-error { background: #fee2e2; color: #991b1b; }

/* Hero / search */
.hero { text-align: center; padding: 40px 0 30px; }
.hero h1 { font-size: 28px; margin-bottom: 20px; }
.search-form { display: flex; gap: 10px; justify-content: center; flex-wrap: wrap; }
.search-form input, .search-form select { padding: 10px 14px; border: 1px solid var(--border); border-radius: 8px; font-size: 14px; }
.search-form input { min-width: 240px; }

/* Buttons */
.btn { display: inline-block; background: var(--primary); color: #fff; border: none; padding: 10px 20px; border-radius: 8px; font-size: 14px; font-weight: 600; cursor: pointer; }
.btn:hover { background: var(--primary-dark); text-decoration: none; }
.btn:disabled { background: #a3a3a3; cursor: not-allowed; }
.btn-block { display: block; width: 100%; text-align: center; }

/* Course grid */
.course-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 20px; margin-top: 10px; }
.course-card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; color: var(--text); transition: box-shadow .15s, transform .15s; }
.course-card:hover { box-shadow: 0 8px 20px rgba(0,0,0,.08); transform: translateY(-2px); text-decoration: none; }
.course-thumb { aspect-ratio: 16/9; background: #eef0f5; overflow: hidden; }
.course-thumb img { width: 100%; height: 100%; object-fit: cover; }
.thumb-placeholder { width: 100%; height: 100%; display: flex; align-items: center; justify-content: center; font-size: 40px; font-weight: 700; color: #fff; background: var(--primary); }
.course-body { padding: 14px 16px; }
.course-category { font-size: 12px; color: var(--primary); font-weight: 600; text-transform: uppercase; }
.course-body h3 { margin: 6px 0; font-size: 16px; }
.course-instructor { font-size: 13px; color: var(--muted); margin: 0 0 6px; }
.course-price { font-weight: 700; margin: 0; }
.course-price.big { font-size: 22px; margin-bottom: 14px; }
.empty-state { grid-column: 1/-1; text-align: center; color: var(--muted); padding: 40px 0; }

/* Course detail */
.course-detail { display: grid; grid-template-columns: 2fr 1fr; gap: 30px; margin-top: 10px; }
.course-description { margin: 16px 0; }
.lesson-list { list-style: none; padding: 0; border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.lesson-list li { border-bottom: 1px solid var(--border); padding: 12px 16px; }
.lesson-list li:last-child { border-bottom: none; }
.lesson-list a { color: var(--text); font-weight: 500; }
.locked { color: var(--muted); }
.course-sidebar { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; height: fit-content; }
.sidebar-thumb { width: 100%; border-radius: 8px; margin-bottom: 14px; }
@media (max-width: 760px) { .course-detail { grid-template-columns: 1fr; } }

/* Progress bar */
.progress-bar { background: #eef0f5; border-radius: 6px; height: 8px; overflow: hidden; margin: 8px 0 4px; }
.progress-fill { background: var(--primary); height: 100%; }

/* Lesson view */
.lesson-view { max-width: 760px; margin: 0 auto; }
.video-wrap { position: relative; padding-top: 56.25%; margin: 18px 0; border-radius: var(--radius); overflow: hidden; background: #000; }
.video-wrap iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }
.lesson-content { margin: 20px 0; }
.lesson-actions { margin: 24px 0; }
.lesson-nav { display: flex; justify-content: space-between; border-top: 1px solid var(--border); padding-top: 16px; margin-top: 20px; }

/* Auth */
.auth-box { max-width: 380px; margin: 30px auto; background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px; }
.auth-box h2 { margin-top: 0; }
.auth-box label { display: block; font-size: 13px; font-weight: 600; margin: 14px 0 6px; }
.auth-box input { width: 100%; padding: 10px 12px; border: 1px solid var(--border); border-radius: 8px; font-size: 14px; }
.auth-switch { text-align: center; margin-top: 16px; font-size: 14px; }

/* Tables (also used in admin) */
.table-wrap { overflow-x: auto; }
.data-table { width: 100%; border-collapse: collapse; background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.data-table th, .data-table td { padding: 10px 14px; text-align: left; border-bottom: 1px solid var(--border); font-size: 14px; }
.data-table th { background: #f3f4f8; font-weight: 600; }

/* Footer */
.site-footer { border-top: 1px solid var(--border); padding: 20px 0; text-align: center; color: var(--muted); font-size: 13px; }