:root {
    --color-bg: #ffffff;
    --color-surface: #f7f8fa;
    --color-text: #1a1d23;
    --color-text-muted: #5b6472;
    --color-border: #e5e8ec;
    --color-primary: #4f46e5;
    --color-primary-hover: #4338ca;
    --color-success-bg: #ecfdf5;
    --color-success-text: #047857;
    --color-error-bg: #fef2f2;
    --color-error-text: #b91c1c;
    --radius-sm: 8px;
    --radius-md: 14px;
    --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06);
    --shadow-md: 0 8px 24px rgba(16, 24, 40, 0.08);
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
}

[data-theme="dark"] {
    --color-bg: #121317;
    --color-surface: #1a1c22;
    --color-text: #f2f3f5;
    --color-text-muted: #9aa0ac;
    --color-border: #2a2d35;
    --color-primary: #6366f1;
    --color-primary-hover: #818cf8;
    --color-success-bg: #052e21;
    --color-success-text: #34d399;
    --color-error-bg: #2c1111;
    --color-error-text: #f87171;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.5);
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: var(--font-sans);
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.55;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 1120px;
    margin: 0 auto;
    padding: 0 24px;
}

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

.site-header {
    border-bottom: 1px solid var(--color-border);
    background: var(--color-bg);
    position: sticky;
    top: 0;
    z-index: 20;
}

.site-header__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
    padding-top: 16px;
    padding-bottom: 16px;
}

.brand { font-weight: 700; font-size: 1.15rem; color: var(--color-text); }

.main-nav { display: flex; align-items: center; gap: 20px; }
.main-nav a:not(.btn) { color: var(--color-text-muted); font-weight: 500; }
.main-nav a:not(.btn):hover { color: var(--color-text); }

.btn {
    display: inline-block;
    padding: 10px 18px;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 0.95rem;
    border: 1px solid transparent;
    cursor: pointer;
}
.btn--primary { background: var(--color-primary); color: #fff; }
.btn--primary:hover { background: var(--color-primary-hover); color: #fff; }
.btn--secondary { background: var(--color-surface); color: var(--color-text); border-color: var(--color-border); }

.theme-toggle {
    background: transparent;
    border: 1px solid var(--color-border);
    border-radius: 999px;
    width: 38px;
    height: 38px;
    font-size: 1rem;
}

.hero { padding: 96px 24px; text-align: center; }
.hero h1 { font-size: clamp(2rem, 4vw, 3rem); margin-bottom: 16px; }
.hero__subtitle { color: var(--color-text-muted); max-width: 620px; margin: 0 auto 32px; }
.hero__actions { display: flex; gap: 12px; justify-content: center; }

.alert { margin: 16px auto; padding: 12px 16px; border-radius: var(--radius-sm); }
.alert--success { background: var(--color-success-bg); color: var(--color-success-text); }
.alert--error { background: var(--color-error-bg); color: var(--color-error-text); }

.error-page { padding: 96px 24px; text-align: center; }
.error-page h1 { font-size: 3rem; margin-bottom: 8px; }

.site-footer {
    border-top: 1px solid var(--color-border);
    color: var(--color-text-muted);
    padding: 24px 0;
    margin-top: 64px;
    font-size: 0.9rem;
}

/* ---------- Shared utility ---------- */
.text-muted { color: var(--color-text-muted); }
.section-heading { margin-top: 40px; margin-bottom: 16px; font-size: 1.3rem; }
.btn--block { display: block; width: 100%; text-align: center; }
.btn-link { background: none; border: none; color: var(--color-primary); cursor: pointer; padding: 0; font-size: 0.9rem; }
.btn-link--danger { color: var(--color-error-text); }

/* ---------- Dashboard ---------- */
.dashboard { padding: 48px 24px; }
.dashboard__header { display: flex; align-items: center; justify-content: space-between; margin-bottom: 24px; flex-wrap: wrap; gap: 12px; }

.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 16px; margin: 24px 0; }
.stat-card { background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 20px; text-align: center; }
.stat-card__value { display: block; font-size: 1.8rem; font-weight: 700; }
.stat-card__label { color: var(--color-text-muted); font-size: 0.85rem; }

.data-table { width: 100%; border-collapse: collapse; margin-bottom: 16px; }
.data-table th, .data-table td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--color-border); font-size: 0.92rem; }
.data-table th { color: var(--color-text-muted); font-weight: 600; }
.row-actions { display: flex; gap: 12px; align-items: center; }
.row-actions form { display: inline; }

.badge { display: inline-block; padding: 3px 10px; border-radius: 999px; font-size: 0.78rem; font-weight: 600; }
.badge--draft { background: #e5e8ec; color: #444; }
.badge--pending { background: #fef3c7; color: #92400e; }
.badge--published { background: var(--color-success-bg); color: var(--color-success-text); }
.badge--unpublished { background: var(--color-error-bg); color: var(--color-error-text); }
.badge--archived { background: #e5e8ec; color: #666; }

.filter-tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 24px; }
.filter-tab { padding: 8px 14px; border-radius: 999px; border: 1px solid var(--color-border); color: var(--color-text-muted); font-size: 0.88rem; }
.filter-tab--active { background: var(--color-primary); color: #fff; border-color: var(--color-primary); }

/* ---------- Cards / catalog ---------- */
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 20px; margin: 20px 0; }
.course-card { display: block; background: var(--color-bg); border: 1px solid var(--color-border); border-radius: var(--radius-md); overflow: hidden; box-shadow: var(--shadow-sm); color: var(--color-text); }
.course-card__body { padding: 18px; }
.course-card h3 { margin: 0 0 6px; font-size: 1.05rem; }
.course-card__price { font-weight: 700; margin-top: 10px; }

.progress-bar { background: var(--color-surface); border-radius: 999px; height: 8px; overflow: hidden; margin: 10px 0 4px; }
.progress-bar__fill { background: var(--color-primary); height: 100%; }

/* ---------- Forms ---------- */
.form { display: flex; flex-direction: column; gap: 6px; }
.form label { font-weight: 600; font-size: 0.88rem; margin-top: 10px; }
.form input[type="text"], .form input[type="email"], .form input[type="password"],
.form input[type="number"], .form input[type="url"], .form select, .form textarea {
    padding: 10px 12px; border: 1px solid var(--color-border); border-radius: var(--radius-sm);
    background: var(--color-bg); color: var(--color-text); font-size: 0.95rem; font-family: inherit;
}
.form--card { background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 24px; }
.form--inline { flex-direction: row; flex-wrap: wrap; align-items: center; gap: 8px; margin-top: 10px; }
.form--inline input, .form--inline select, .form--inline textarea { flex: 1 1 160px; margin-top: 0; }
.checkbox-row { display: flex; align-items: center; gap: 8px; font-weight: 500; }

.auth-page { padding: 72px 24px; display: flex; justify-content: center; }
.auth-card { width: 100%; max-width: 420px; background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 32px; }
.auth-switch { margin-top: 16px; text-align: center; color: var(--color-text-muted); }

/* ---------- Course builder ---------- */
.builder-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; margin-top: 24px; }
.section-card { border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 16px; margin-bottom: 16px; background: var(--color-surface); }
.section-card__header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 8px; }
.lesson-list { list-style: none; padding: 0; margin: 0 0 10px; }
.lesson-list li { display: flex; justify-content: space-between; padding: 6px 0; border-bottom: 1px solid var(--color-border); }
.checklist { padding-left: 20px; }
.checklist li { margin-bottom: 6px; }
.prose { line-height: 1.7; }

.filter-bar { display: flex; gap: 10px; flex-wrap: wrap; margin: 20px 0; }
.filter-bar input, .filter-bar select { padding: 10px 12px; border: 1px solid var(--color-border); border-radius: var(--radius-sm); background: var(--color-bg); color: var(--color-text); }

/* ---------- Course detail ---------- */
.course-detail { display: grid; grid-template-columns: 2fr 1fr; gap: 40px; padding: 48px 24px; align-items: start; }
.course-detail__lead { font-size: 1.1rem; color: var(--color-text-muted); }
.course-detail__price-card { background: var(--color-surface); border: 1px solid var(--color-border); border-radius: var(--radius-md); padding: 24px; position: sticky; top: 90px; }

@media (max-width: 860px) {
    .builder-grid, .course-detail { grid-template-columns: 1fr; }
}

/* ---------- Learning interface ---------- */
.learn-header { display: flex; justify-content: space-between; align-items: center; padding: 14px 24px; border-bottom: 1px solid var(--color-border); background: var(--color-bg); }
.learn-header__back, .learn-header__exit { color: var(--color-text-muted); font-weight: 600; font-size: 0.9rem; }
.learn-layout { display: grid; grid-template-columns: 300px 1fr; min-height: calc(100vh - 60px); }
.learn-sidebar { border-right: 1px solid var(--color-border); padding: 20px; overflow-y: auto; }
.learn-sidebar__section { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.04em; color: var(--color-text-muted); margin: 18px 0 8px; }
.learn-sidebar__lessons { list-style: none; padding: 0; margin: 0; }
.learn-sidebar__lessons a { display: flex; gap: 8px; align-items: center; padding: 8px 10px; border-radius: var(--radius-sm); color: var(--color-text); font-size: 0.9rem; }
.learn-sidebar__lessons a.is-active { background: var(--color-surface); color: var(--color-primary); font-weight: 600; }
.lesson-check { width: 16px; color: var(--color-success-text); font-weight: 700; }
.learn-content { padding: 32px; max-width: 760px; }
.learn-actions { margin-top: 28px; }
.video-embed { position: relative; padding-bottom: 56.25%; height: 0; margin: 16px 0; }
.video-embed iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 0; border-radius: var(--radius-md); }
.video-native { width: 100%; border-radius: var(--radius-md); margin: 16px 0; }

@media (max-width: 860px) {
    .learn-layout { grid-template-columns: 1fr; }
    .learn-sidebar { border-right: none; border-bottom: 1px solid var(--color-border); }
}

/* ---------- Certificate ---------- */
.certificate-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 24px;
    border-bottom: 1px solid var(--color-border);
}
.certificate-page {
    display: flex;
    justify-content: center;
    padding: 48px 24px;
}
.certificate {
    width: 100%;
    max-width: 820px;
    border: 3px double var(--color-primary);
    border-radius: var(--radius-md);
    padding: 64px 56px;
    text-align: center;
    background: var(--color-bg);
}
.certificate__eyebrow {
    text-transform: uppercase;
    letter-spacing: 0.12em;
    color: var(--color-text-muted);
    font-size: 0.8rem;
    font-weight: 700;
    margin-bottom: 24px;
}
.certificate__title {
    font-size: 2.2rem;
    margin: 0 0 24px;
}
.certificate__lead {
    color: var(--color-text-muted);
    margin: 4px 0;
}
.certificate__name {
    font-size: 1.8rem;
    font-weight: 700;
    margin: 8px 0 16px;
    color: var(--color-primary);
}
.certificate__course {
    font-size: 1.3rem;
    font-weight: 600;
    margin: 8px 0 32px;
}
.certificate__meta {
    display: flex;
    justify-content: center;
    gap: 64px;
    margin: 24px 0;
}
.certificate__meta-label {
    text-transform: uppercase;
    font-size: 0.75rem;
    letter-spacing: 0.06em;
    color: var(--color-text-muted);
    margin-bottom: 4px;
}
.certificate__number {
    margin-top: 32px;
    font-family: monospace;
    color: var(--color-text-muted);
}
.certificate__verify {
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

@media print {
    .no-print { display: none !important; }
    .certificate-page { padding: 0; }
    .certificate { border-width: 2px; box-shadow: none; }
    body { background: #fff; }
}