/* ===== Thiết lập chung ===== */
:root {
    --xanh-dam: #12304a;
    --xanh-vua: #1f5a7a;
    --vang: #f0b429;
    --nen: #eef3f6;
    --trang: #ffffff;
    --chu: #1b2b38;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    font-family: "Be Vietnam Pro", Arial, sans-serif;
    background: var(--nen);
    color: var(--chu);
    line-height: 1.6;
}

/* ===== Đầu trang ===== */
header {
    background: var(--xanh-dam);
    color: var(--trang);
    text-align: center;
    padding: 40px 20px 28px;
}

header h1 {
    margin: 0;
    font-size: 2.4rem;
    font-weight: 800;
    letter-spacing: 3px;
}

header p {
    margin: 8px 0 0;
    color: #c8d9e5;
}

/* ===== Thanh menu ===== */
nav {
    position: sticky;
    top: 0;
    z-index: 10;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    background: var(--xanh-vua);
}

nav a {
    color: var(--trang);
    text-decoration: none;
    padding: 14px 22px;
    font-weight: 600;
    border-bottom: 3px solid transparent;
}

nav a:hover,
nav a:focus-visible {
    border-bottom-color: var(--vang);
    background: rgba(255, 255, 255, 0.08);
    outline: none;
}

/* ===== Nội dung ===== */
main {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
}

section {
    padding: 32px 0 8px;
    scroll-margin-top: 60px;
}

h2 {
    color: var(--xanh-dam);
    font-size: 1.7rem;
    margin: 0 0 6px;
    padding-left: 12px;
    border-left: 6px solid var(--vang);
}

h3 {
    margin: 0 0 6px;
    font-size: 1.05rem;
    color: var(--xanh-vua);
}

/* Banner trang chủ */
.banner {
    background: linear-gradient(135deg, var(--xanh-dam), var(--xanh-vua));
    color: var(--trang);
    border-radius: 14px;
    padding: 48px 32px;
    margin-top: 12px;
    text-align: center;
}

.banner h2 {
    color: var(--trang);
    border: none;
    padding: 0;
    font-size: 2.2rem;
}

.nut {
    display: inline-block;
    margin-top: 12px;
    background: var(--vang);
    color: var(--xanh-dam);
    font-weight: 800;
    text-decoration: none;
    padding: 10px 26px;
    border-radius: 30px;
}

.nut:hover,
.nut:focus-visible {
    background: #ffd166;
}

/* ===== Lưới thẻ bài hát / video ===== */
.luoi {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 16px;
    margin-top: 16px;
}

.bai-hat,
.video-the {
    background: var(--trang);
    border-radius: 10px;
    padding: 16px;
    box-shadow: 0 2px 8px rgba(18, 48, 74, 0.12);
}

.ghi-chu {
    margin: 0 0 10px;
    font-size: 0.9rem;
    color: #5b6e7c;
}

audio,
video,
iframe {
    width: 100%;
    border-radius: 8px;
}

iframe {
    aspect-ratio: 16 / 9;
    border: 0;
}

/* ===== Bảng ===== */
.bang-boc {
    overflow-x: auto;
    margin-top: 16px;
}

table {
    width: 100%;
    border-collapse: collapse;
    background: var(--trang);
}

th,
td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid #d6e0e7;
}

th {
    background: var(--xanh-dam);
    color: var(--trang);
}

tbody tr:nth-child(even) { background: #f6f9fb; }
tbody tr:hover { background: #fff6dc; }

/* ===== Chân trang ===== */
footer {
    margin-top: 40px;
    background: var(--xanh-dam);
    color: #c8d9e5;
    text-align: center;
    padding: 18px;
}

footer p { margin: 0; }

/* ===== Màn hình nhỏ (điện thoại) ===== */
@media (max-width: 600px) {
    header h1 { font-size: 1.6rem; letter-spacing: 1px; }
    nav a { padding: 10px 14px; }
    .banner { padding: 32px 18px; }
    .banner h2 { font-size: 1.6rem; }
}