/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Solarized Light Color Scheme */
    --base03: #002b36;
    --base02: #073642;
    --base01: #586e75;
    --base00: #657b83;
    --base0: #839496;
    --base1: #93a1a1;
    --base2: #eee8d5;
    --base3: #fdf6e3;
    --yellow: #b58900;
    --orange: #cb4b16;
    --red: #dc322f;
    --magenta: #d33682;
    --violet: #6c71c4;
    --blue: #268bd2;
    --cyan: #2aa198;
    --green: #859900;

    /* Application Colors */
    --primary-color: var(--blue);
    --secondary-color: var(--base01);
    --background: var(--base3);
    --surface: var(--base2);
    --border: var(--base1);
    --text-primary: var(--base01);
    --text-secondary: var(--base00);
    --beginner: var(--green);
    --intermediate: var(--yellow);
    --advanced: var(--orange);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background-color: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 40px 0;
    margin-bottom: 40px;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
}

header .subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Filters */
.filters {
    display: flex;
    gap: 10px;
    margin-bottom: 30px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 16px;
    border: 1px solid var(--border);
    background-color: var(--background);
    color: var(--text-primary);
    border-radius: 6px;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.2s;
}

.filter-btn:hover {
    background-color: var(--surface);
    border-color: var(--primary-color);
}

.filter-btn.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* Courses Grid */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 24px;
    margin-bottom: 60px;
}

/* Course Card */
.course-card {
    background-color: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
    transition: transform 0.2s, box-shadow 0.2s;
}

.course-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 12px;
}

.course-title {
    font-size: 1.4rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.course-level {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    white-space: nowrap;
}

.level-beginner {
    background-color: rgba(40, 167, 69, 0.1);
    color: var(--beginner);
}

.level-intermediate {
    background-color: rgba(255, 211, 61, 0.2);
    color: #735c0f;
}

.level-advanced {
    background-color: rgba(246, 106, 10, 0.1);
    color: var(--advanced);
}

.course-description {
    color: var(--text-secondary);
    margin-bottom: 16px;
    line-height: 1.5;
}

.course-meta {
    display: flex;
    gap: 16px;
    margin-bottom: 16px;
    font-size: 14px;
    color: var(--text-secondary);
}

.course-meta-item {
    display: flex;
    align-items: center;
    gap: 6px;
}

.topics {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-bottom: 16px;
}

.topic-tag {
    background-color: var(--background);
    border: 1px solid var(--border);
    padding: 4px 10px;
    border-radius: 12px;
    font-size: 12px;
    color: var(--text-secondary);
}

.course-link {
    display: inline-block;
    padding: 8px 16px;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-weight: 500;
    transition: background-color 0.2s;
}

.course-link:hover {
    background-color: #0256c7;
}

/* Footer */
footer {
    background-color: var(--surface);
    border-top: 1px solid var(--border);
    padding: 30px 0;
    text-align: center;
    color: var(--text-secondary);
}

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

footer a:hover {
    text-decoration: underline;
}

/* Responsive */
@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .courses-grid {
        grid-template-columns: 1fr;
    }
}