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

:root {
    --bg: #0f1420;
    --surface: #171e2e;
    --surface-2: #1f2940;
    --text: #e8ecf4;
    --muted: #9aa7bd;
    --accent: #ffb454;
    --radius: 14px;
}

body {
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    width: min(1100px, 92%);
    margin: 0 auto;
}

.site-header {
    background: var(--surface);
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
    padding: 16px 0;
}

.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 12px;
}

.brand {
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--text);
    text-decoration: none;
    letter-spacing: 0.5px;
}

.main-nav {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}

.main-nav a {
    color: var(--muted);
    text-decoration: none;
    padding: 8px 14px;
    border-radius: 999px;
    font-size: 0.95rem;
    transition: background 0.15s, color 0.15s;
}

.main-nav a:hover {
    color: var(--text);
    background: var(--surface-2);
}

.main-nav a.active {
    color: var(--bg);
    background: var(--accent);
    font-weight: 600;
}

main {
    flex: 1;
    padding: 48px 0;
}

.hero {
    text-align: center;
    padding: 24px 0 40px;
}

.hero h1 {
    font-size: clamp(1.9rem, 4vw, 3rem);
    margin-bottom: 12px;
    letter-spacing: -0.5px;
}

.hero p {
    color: var(--muted);
    font-size: 1.15rem;
    max-width: 640px;
    margin: 0 auto;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-top: 24px;
}

.course-card {
    background: var(--surface);
    border: 1px solid rgba(255, 255, 255, 0.07);
    border-radius: var(--radius);
    padding: 28px;
    text-decoration: none;
    color: var(--text);
    display: flex;
    flex-direction: column;
    gap: 12px;
    transition: transform 0.15s, border-color 0.15s, box-shadow 0.15s;
}

.course-card:hover {
    transform: translateY(-4px);
    border-color: var(--card-color, var(--accent));
    box-shadow: 0 12px 32px rgba(0, 0, 0, 0.35);
}

.course-card .flag {
    font-size: 2.6rem;
}

.course-card h2 {
    font-size: 1.5rem;
}

.course-card .native {
    color: var(--muted);
}

.course-card .badge {
    align-self: flex-start;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--bg);
    background: var(--card-color, var(--accent));
    padding: 4px 12px;
    border-radius: 999px;
}

.course-card p {
    color: var(--muted);
    font-size: 0.95rem;
    flex: 1;
}

/* Course detail page */
.course-hero {
    background: var(--surface);
    border: 1px solid rgba(255, 255, 255, 0.07);
    border-radius: var(--radius);
    padding: 32px;
    margin-bottom: 32px;
}

.course-hero .flag {
    font-size: 3rem;
}

.course-hero h1 {
    font-size: clamp(1.6rem, 3vw, 2.4rem);
    margin: 8px 0 4px;
}

.course-hero .native {
    color: var(--muted);
}

.course-hero .intro {
    color: var(--muted);
    margin-top: 12px;
    max-width: 720px;
}

.course-meta {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    margin-top: 16px;
    font-size: 0.9rem;
    color: var(--muted);
}

.course-meta span {
    background: var(--surface-2);
    padding: 6px 12px;
    border-radius: 999px;
}

.section {
    background: var(--surface);
    border: 1px solid rgba(255, 255, 255, 0.07);
    border-radius: var(--radius);
    padding: 24px;
    margin-bottom: 20px;
}

.section h2 {
    font-size: 1.3rem;
    margin-bottom: 16px;
    color: var(--accent);
}

.lesson {
    display: flex;
    gap: 12px;
    padding: 10px 0;
    border-bottom: 1px dashed rgba(255, 255, 255, 0.08);
}

.lesson:last-child {
    border-bottom: none;
}

.lesson .key {
    flex: 0 0 230px;
    font-weight: 600;
}

.lesson .value {
    color: var(--muted);
}

.callout {
    background: var(--surface-2);
    border-left: 4px solid var(--accent);
    padding: 16px 20px;
    border-radius: 0 10px 10px 0;
    margin-top: 28px;
    color: var(--muted);
}

.not-found {
    text-align: center;
    padding: 60px 0;
}

.not-found h1 {
    margin-bottom: 12px;
}

.btn {
    display: inline-block;
    margin-top: 16px;
    background: var(--accent);
    color: var(--bg);
    font-weight: 600;
    text-decoration: none;
    padding: 10px 22px;
    border-radius: 999px;
}

.site-footer {
    border-top: 1px solid rgba(255, 255, 255, 0.06);
    padding: 20px 0;
    color: var(--muted);
    font-size: 0.9rem;
}

@media (max-width: 640px) {
    main {
        padding: 28px 0;
    }
    .lesson {
        flex-direction: column;
        gap: 4px;
    }
    .lesson .key {
        flex: none;
    }
}