:root {
    --blue: #007aff;
    --gray: #333;
    --bg: #f9f9f9;
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    margin: 0;
    padding: 0;
    background: var(--bg);
    color: var(--gray);
    line-height: 1.6;
}
main {
    max-width: 720px;
    padding: 2rem;
    margin: auto;
}
header, footer {
    text-align: center;
    padding: 1.5rem 1rem;
    background: white;
    box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}
h1 {
    font-size: 2rem;
    margin-bottom: 0.25rem;
}
nav a {
    margin: 0 1rem;
    text-decoration: none;
    color: var(--blue);
}
nav a:hover {
    text-decoration: underline;
}
footer a {
    text-decoration: none;
    color: var(--blue);
}
footer a:hover {
    text-decoration: underline;
}
ul {
    padding-left: 1.2rem;
}
@media (max-width: 600px) {
    main {
        padding: 1rem;
    }
    nav a {
        display: inline-block;
        margin: 0.5rem;
    }
}