:root {
    --bg: #f8f9fa;
    --text: #222;
    --muted: #666;
    --link: #1f4f7a;
    --button-bg: #ffffff;
    --button-border: #ddd;
}

html[data-theme="dark"] {
    --bg: #111316;
    --text: #f2f2f2;
    --muted: #b8b8b8;
    --link: #8ab4f8;
    --button-bg: #1b1f24;
    --button-border: #333;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--text);
    transition: background 0.2s ease, color 0.2s ease;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    text-align: center;
    padding: 3rem 1rem;
}

h1 {
    font-size: 3.5rem;
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--muted);
    font-size: 1.2rem;
    margin-bottom: 2rem;
}

.video iframe {
    width: 100%;
    max-width: 900px;
    aspect-ratio: 16 / 9;
    border: none;
}

nav {
    margin-top: 2rem;
}

nav a {
    margin: 0 1rem;
    color: var(--link);
    text-decoration: none;
    font-weight: 500;
}

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

#theme-toggle {
    position: fixed;
    top: 1rem;
    right: 1rem;
    width: 2.4rem;
    height: 2.4rem;
    border-radius: 50%;
    border: 1px solid var(--button-border);
    background: var(--button-bg);
    color: var(--text);
    font-size: 1.2rem;
    cursor: pointer;
}