:root {
    --bg: #f4f6f9;
    --card: #ffffff;
    --text: #1f2937;
    --muted: #6b7280;
    --border: #e5e7eb;
    --accent: #2563eb;
    --radius: 16px;
    --shadow: 0 20px 45px rgba(0, 0, 0, 0.08);
    --max-width: 820px;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #0f172a;
        --card: #111827;
        --text: #e5e7eb;
        --muted: #9ca3af;
        --border: #1f2937;
        --accent: #60a5fa;
        --shadow: 0 25px 60px rgba(0, 0, 0, 0.45);
    }
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 50px 20px;
    font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
}

/* Centered card */
main {
    max-width: var(--max-width);
    margin: 0 auto;
    background: var(--card);
    padding: 50px 60px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

/* Typography */
h1 {
    font-size: 2rem;
    margin-top: 0;
    margin-bottom: 10px;
    text-align: center;
    border-bottom: 1px solid var(--border);
    padding-bottom: 20px;
}

h2 {
    margin-top: 40px;
    font-size: 1.25rem;
    position: relative;
}

h2::after {
    content: "";
    display: block;
    width: 60px;
    height: 3px;
    margin-top: 8px;
    background: var(--accent);
    border-radius: 4px;
    opacity: 0.6;
}

p {
    margin: 12px 0;
}

ul {
    margin: 10px 0 20px 20px;
}

li {
    margin-bottom: 8px;
}

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

a:hover {
    text-decoration: underline;
}