:root {
    --bg: #ffffff;
    --text: #0f172a;
    --muted: #64748b;
    --border: #e5e7eb;
    --accent: #2563eb;
    --radius: 10px;
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--text);
    font-family: Inter, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    line-height: 1.6;
}

/* layout */
.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 24px;
}

/* header */
.header {
    border-bottom: 1px solid var(--border);
    background: #fff;
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.brand {
    font-weight: 600;
    font-size: 18px;
    color: var(--text);
    text-decoration: none;
}

.nav-links a {
    margin-right: 16px;
    font-size: 14px;
    color: var(--muted);
    text-decoration: none;
}

.nav-links a:hover {
    color: var(--text);
}

/* search */
.search-input {
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 8px 12px;
    font-size: 14px;
    width: 220px;
    outline: none;
    font-family: inherit;
}

.search-input:focus {
    border-color: var(--accent);
}

/* course list */
.course-card {
    display: flex;
    gap: 20px;
    padding: 20px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 16px;
    transition: background 0.1s;
}

.course-card:hover {
    background: #f9fafb;
}

.course-img {
    width: 140px;
    height: 90px;
    background-color: #f3f4f6;
    border-radius: 6px;
    object-fit: cover;
    flex-shrink: 0;
}

.course-title {
    font-size: 17px;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text);
}

.course-desc {
    font-size: 14px;
    color: var(--muted);
    margin-bottom: 10px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.view-link {
    font-size: 14px;
    color: var(--accent);
    text-decoration: none;
}

.view-link:hover {
    text-decoration: underline;
}

/* detail */
.detail-img {
    width: 100%;
    max-height: 400px;
    object-fit: cover;
    border-radius: var(--radius);
    margin-bottom: 24px;
    border: 1px solid var(--border);
}

h1 {
    font-size: 24px;
    margin-bottom: 16px;
}

.enroll-btn {
    display: inline-block;
    margin-top: 24px;
    padding: 10px 18px;
    background: var(--accent);
    color: #fff;
    border-radius: var(--radius);
    font-size: 14px;
    text-decoration: none;
    font-weight: 500;
}

.enroll-btn:hover {
    background: #1e4fd6;
}

/* footer */
.footer {
    border-top: 1px solid var(--border);
    margin-top: 60px;
    padding: 24px 0;
    text-align: center;
    font-size: 13px;
    color: var(--muted);
}