:root {
    --text-main: #111;
    --text-muted: #555;
    --max-width: 640px;
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 72px 24px;
    font-family: "IBM Plex Serif", serif;
    font-size: 17.5px; /* giảm nhẹ */
    line-height: 1.85; /* tăng nhịp thở */
    letter-spacing: 0.01em; /* giúp chữ Việt thoáng hơn */
    word-spacing: 0.05em; /* rất quan trọng cho tiếng Việt */
    color: var(--text-main);
    background: #fff;
    text-rendering: optimizeLegibility;
}

main,
article {
    max-width: var(--max-width);
    margin: 0 auto;
}

h1 {
    font-size: 30px;
    font-weight: 500;
    line-height: 1.3;
    margin-bottom: 36px;
}

h2 {
    font-size: 21px;
    font-weight: 500;
    line-height: 1.4;
    margin-top: 56px;
    margin-bottom: 18px;
}

p {
    margin: 0 0 28px 0;
}

a {
    color: inherit;
    text-decoration: none;
    border-bottom: 1px solid #e0e0e0;
}

a:hover {
    border-bottom-color: #999;
}

nav {
    margin-top: 48px;
    font-size: 16px;
    color: var(--text-muted);
}