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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.site-header {
    background: #fff;
    border-bottom: 1px solid #e5e5e5;
    padding: 16px 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.site-logo {
    font-size: 20px;
    font-weight: 700;
    color: #1e293b;
    text-decoration: none;
}

.site-nav {
    display: flex;
    gap: 20px;
    align-items: center;
}

.site-nav a {
    color: #475569;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
}

.site-nav a:hover {
    color: #4a90e2;
}

.btn-nav {
    background: #4a90e2;
    color: #fff !important;
    padding: 8px 16px;
    border-radius: 4px;
}

/* Main */
.site-main {
    padding: 40px 0;
    min-height: 60vh;
}

/* Hero */
.hero {
    text-align: center;
    padding: 60px 20px;
    background: #fff;
    border-radius: 8px;
    margin-bottom: 40px;
}

.hero h1 {
    font-size: 36px;
    margin-bottom: 12px;
    color: #1e293b;
}

.hero p {
    font-size: 16px;
    color: #64748b;
    margin-bottom: 24px;
}

/* Section */
.section-title {
    font-size: 24px;
    margin-bottom: 20px;
    color: #1e293b;
}

.page-title {
    font-size: 28px;
    margin-bottom: 24px;
    color: #1e293b;
}

/* Courses grid */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 24px;
}

.course-card {
    background: #fff;
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0,0,0,0.08);
    transition: transform 0.2s, box-shadow 0.2s;
}

.course-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.12);
}

.course-thumb {
    height: 160px;
    background: #e2e8f0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.course-thumb img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.course-thumb-placeholder {
    font-size: 48px;
}

.course-thumb-placeholder.large {
    font-size: 80px;
}

.course-body {
    padding: 16px;
}

.course-body h3 {
    font-size: 16px;
    margin-bottom: 8px;
    color: #1e293b;
}

.course-desc {
    font-size: 13px;
    color: #64748b;
    margin-bottom: 16px;
}

.course-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.course-price {
    font-size: 18px;
    font-weight: 700;
    color: #4a90e2;
}

/* Course detail */
.course-detail {
    background: #fff;
    border-radius: 8px;
    padding: 30px;
}

.course-detail-header {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 30px;
    margin-bottom: 30px;
}

.course-thumb-large {
    height: 300px;
    background: #e2e8f0;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.course-thumb-large img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.course-detail-info h1 {
    font-size: 28px;
    margin-bottom: 16px;
}

.course-price-large {
    font-size: 32px;
    font-weight: 700;
    color: #4a90e2;
    margin-bottom: 20px;
}

.btn-large {
    padding: 14px 32px;
    font-size: 16px;
}

.course-detail-body {
    border-top: 1px solid #e5e5e5;
    padding-top: 24px;
}

.course-detail-body h2 {
    font-size: 20px;
    margin-bottom: 12px;
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 10px 20px;
    border: none;
    border-radius: 4px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    text-decoration: none;
    transition: background 0.2s;
}

.btn-primary {
    background: #4a90e2;
    color: #fff;
}

.btn-primary:hover {
    background: #357abd;
}

/* Alerts */
.alert {
    padding: 12px;
    border-radius: 4px;
    margin-bottom: 16px;
    font-size: 14px;
}

.alert-error {
    background: #fee;
    color: #c33;
    border: 1px solid #fcc;
}

.alert-success {
    background: #efe;
    color: #3c3;
    border: 1px solid #cfc;
}

/* Footer */
.site-footer {
    background: #1e293b;
    color: #94a3b8;
    padding: 20px 0;
    text-align: center;
    font-size: 14px;
    margin-top: 60px;
}

/* Auth pages */
.auth-container {
    min-height: 60vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.auth-box {
    background: #fff;
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    width: 100%;
    max-width: 400px;
}

.auth-box h1 {
    margin-bottom: 24px;
    font-size: 24px;
    text-align: center;
}

.form-group {
    margin-bottom: 16px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    font-weight: 500;
    font-size: 14px;
}

.form-group input {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 14px;
}

.form-group input:focus {
    outline: none;
    border-color: #4a90e2;
}

.btn-primary.full-width {
    width: 100%;
}

.auth-link {
    text-align: center;
    margin-top: 20px;
    font-size: 14px;
}

.auth-link a {
    color: #4a90e2;
    text-decoration: none;
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 { font-size: 24px; }
    .course-detail-header { grid-template-columns: 1fr; }
    .site-nav { gap: 10px; font-size: 12px; }
}