:root {
    --bg-color: #1a1a1a;
    --text-color: #e0e0e0;
    --accent-color: #007BFF;
    --secondary-color: #28A745;
    --card-bg: #2a2a2a;
}

.light-mode {
    --bg-color: #ffffff;
    --text-color: #333333;
    --accent-color: #0056b3;
    --secondary-color: #1e7e34;
    --card-bg: #f8f9fa;
}

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    line-height: 1.6;
    transition: background 0.3s, color 0.3s;
}

header { background: var(--card-bg); padding: 1rem 0; position: sticky; top: 0; z-index: 10; }
.navbar { display: flex; justify-content: space-between; align-items: center; max-width: 1200px; margin: 0 auto; padding: 0 1rem; }
.nav-brand { font-size: 1.5rem; font-weight: 600; color: var(--accent-color); }
.nav-menu { display: flex; list-style: none; gap: 2rem; margin: 0; padding: 0; }
.nav-menu a { color: var(--text-color); text-decoration: none; transition: color 0.3s; }
.nav-menu a:hover { color: var(--accent-color); }
.mode-toggle { font-size: 1.5rem; cursor: pointer; }

.section { padding: 4rem 1rem; max-width: 1200px; margin: 0 auto; }
.hero { text-align: center; padding: 6rem 1rem; background: linear-gradient(to right, var(--accent-color), var(--secondary-color)); color: white; }
.hero h1 { font-size: 3rem; margin: 0; }
.hero h2 { font-size: 1.5rem; margin: 0.5rem 0; }
.profile-img { border-radius: 50%; margin: 1rem; }
.cta-btn { background: white; color: var(--accent-color); padding: 0.8rem 2rem; text-decoration: none; border-radius: 5px; font-weight: 600; transition: background 0.3s; }
.cta-btn:hover { background: #f0f0f0; }

.bio, .certs { background: var(--card-bg); padding: 2rem; border-radius: 8px; margin: 1rem 0; }
.certs { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 1rem; list-style: none; padding: 0; }
.certs li { background: var(--bg-color); padding: 0.5rem; border-radius: 4px; }
.links { text-align: center; margin: 1rem 0; }
.links a { color: var(--accent-color); }

.tutorial-categories { display: grid; gap: 3rem; }
.category { margin-bottom: 2rem; }
.category h3 { color: var(--accent-color); border-bottom: 2px solid var(--secondary-color); padding-bottom: 0.5rem; }
.video-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 1.5rem; }
.video-item { background: var(--card-bg); border-radius: 8px; overflow: hidden; }
.video-item iframe { width: 100%; height: 200px; }
.video-item p { padding: 1rem; margin: 0; font-family: 'JetBrains Mono', monospace; }

.contact-form { max-width: 600px; margin: 2rem auto; display: grid; gap: 1rem; }
.contact-form input, .contact-form textarea { padding: 0.8rem; border: 1px solid var(--accent-color); border-radius: 4px; background: var(--bg-color); color: var(--text-color); }
.contact-form button { background: var(--accent-color); color: white; border: none; padding: 0.8rem; border-radius: 4px; cursor: pointer; font-weight: 600; }

footer { text-align: center; padding: 2rem; background: var(--card-bg); }

@media (max-width: 768px) {
    .nav-menu { flex-direction: column; gap: 1rem; }
    .hero h1 { font-size: 2rem; }
    .video-grid { grid-template-columns: 1fr; }
}