:root {
    --primary: #1a1a2e;
    --secondary: #16213e;
    --accent: #00b4d8;
    --text: #e0e0e0;
    --card-bg: rgba(22, 33, 62, 0.95);
}
* { margin: 0; padding: 0; box-sizing: border-box; }
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, var(--primary) 0%, var(--secondary) 100%);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
}
.header {
    background: rgba(26, 26, 46, 0.95);
    backdrop-filter: blur(10px);
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 180, 216, 0.3);
}
.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
}
.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--accent);
    text-decoration: none;
}
.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    flex-wrap: wrap;
}
.nav-menu a {
    color: var(--text);
    text-decoration: none;
    transition: color 0.3s;
}
.nav-menu a:hover, .nav-menu a.active { color: var(--accent); }
.main-content {
    max-width: 1200px;
    margin: 80px auto 0;
    padding: 2rem;
}
.hero {
    text-align: center;
    padding: 4rem 2rem;
    background: linear-gradient(135deg, rgba(0, 180, 216, 0.1), rgba(0, 0, 0, 0.3));
    border-radius: 20px;
    margin-bottom: 3rem;
}
.hero h1 { font-size: 3rem; margin-bottom: 1rem; }
.section-title {
    font-size: 2rem;
    margin-bottom: 2rem;
    border-left: 4px solid var(--accent);
    padding-left: 1rem;
}
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}
.course-card {
    background: var(--card-bg);
    border-radius: 15px;
    padding: 1.5rem;
    transition: transform 0.3s;
    border: 1px solid rgba(0, 180, 216, 0.2);
}
.course-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent);
}
.course-card h3 { color: var(--accent); margin-bottom: 1rem; }
.course-meta {
    display: flex;
    gap: 1rem;
    margin: 1rem 0;
    font-size: 0.9rem;
}
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: bold;
    transition: all 0.3s;
    cursor: pointer;
    border: none;
}
.btn-primary {
    background: var(--accent);
    color: var(--primary);
}
.btn-primary:hover {
    background: #0077b6;
    transform: translateY(-2px);
}
.btn-outline {
    border: 2px solid var(--accent);
    color: var(--accent);
    background: transparent;
}
.btn-outline:hover {
    background: var(--accent);
    color: var(--primary);
}
.course-content {
    background: var(--card-bg);
    border-radius: 15px;
    padding: 2rem;
}
.course-content pre {
    background: var(--primary);
    padding: 1rem;
    border-radius: 8px;
    overflow-x: auto;
    margin: 1rem 0;
}
.course-content code {
    font-family: 'Courier New', monospace;
    color: var(--accent);
}
.quiz-section {
    margin-top: 2rem;
    padding: 2rem;
    background: var(--card-bg);
    border-radius: 15px;
}
.question {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: rgba(0, 0, 0, 0.3);
    border-radius: 10px;
}
.options { margin: 1rem 0 0 1rem; }
.options label { display: block; margin: 0.5rem 0; cursor: pointer; }
.footer {
    text-align: center;
    padding: 2rem;
    background: var(--primary);
    margin-top: 3rem;
}
.progress-container {
    background: var(--secondary);
    border-radius: 10px;
    height: 10px;
    overflow: hidden;
}
.progress-bar {
    background: var(--accent);
    height: 100%;
    transition: width 0.3s;
}
@media (max-width: 768px) {
    .nav-container { flex-direction: column; gap: 1rem; }
    .hero h1 { font-size: 2rem; }
    .courses-grid { grid-template-columns: 1fr; }
}