/* MegaBox – giao diện chung. Mọi class đều có tiền tố "mb-" để không đụng CSS của trang Piano. */
:root {
    --mb-bg: #f5f6fb;
    --mb-surface: #ffffff;
    --mb-text: #1e2235;
    --mb-muted: #6b7190;
    --mb-border: #e3e6f2;
    --mb-primary: #5b5bf0;
    --mb-primary-dark: #4343d1;
    --mb-accent: #ec4899;
    --mb-danger: #e5484d;
    --mb-radius: 14px;
    --mb-shadow: 0 6px 24px rgba(40, 44, 90, .08);
}

body {
    margin: 0;
    font-family: "Segoe UI", system-ui, -apple-system, Roboto, sans-serif;
    background: var(--mb-bg);
    color: var(--mb-text);
}

[hidden] { display: none !important; }

/* ---------- Thanh điều hướng ---------- */
.mb-nav {
    position: sticky; top: 0; z-index: 50;
    display: flex; align-items: center; gap: 24px;
    padding: 0 24px; height: 60px;
    background: rgba(255, 255, 255, .92); backdrop-filter: blur(8px);
    border-bottom: 1px solid var(--mb-border);
    font-family: "Segoe UI", system-ui, sans-serif;
}
.mb-brand { display: flex; align-items: center; gap: 8px; font-weight: 800; font-size: 20px; color: var(--mb-text); text-decoration: none; }
.mb-brand span { background: linear-gradient(135deg, var(--mb-primary), var(--mb-accent)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.mb-links { display: flex; gap: 4px; flex: 1; }
.mb-links a { padding: 8px 14px; border-radius: 10px; color: var(--mb-muted); text-decoration: none; font-weight: 600; font-size: 14px; }
.mb-links a:hover, .mb-links a.active { background: #eef0ff; color: var(--mb-primary); }
.mb-auth-area { display: flex; align-items: center; gap: 10px; }
.mb-user { display: flex; align-items: center; gap: 10px; font-size: 14px; font-weight: 600; }
.mb-avatar {
    width: 34px; height: 34px; border-radius: 50%; display: grid; place-items: center;
    background: linear-gradient(135deg, var(--mb-primary), var(--mb-accent)); color: #fff; font-weight: 700;
}

/* ---------- Nút ---------- */
.mb-btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 6px;
    padding: 9px 18px; border-radius: 10px; border: 1px solid var(--mb-border);
    background: var(--mb-surface); color: var(--mb-text); font: 600 14px "Segoe UI", system-ui, sans-serif;
    cursor: pointer; text-decoration: none; transition: .15s;
}
.mb-btn:hover { border-color: var(--mb-primary); color: var(--mb-primary); }
.mb-btn-primary { background: var(--mb-primary); border-color: var(--mb-primary); color: #fff; }
.mb-btn-primary:hover { background: var(--mb-primary-dark); border-color: var(--mb-primary-dark); color: #fff; }
.mb-btn-danger:hover { border-color: var(--mb-danger); color: var(--mb-danger); }
.mb-btn-sm { padding: 6px 12px; font-size: 13px; }
.mb-btn-lg { padding: 13px 28px; font-size: 16px; border-radius: 12px; }
.mb-btn:disabled { opacity: .6; cursor: not-allowed; }

/* ---------- Trang chủ ---------- */
.mb-container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }

.mb-hero {
    background: radial-gradient(circle at 15% 20%, #7c7cff 0, transparent 45%),
                radial-gradient(circle at 85% 70%, #ff7ac0 0, transparent 40%),
                linear-gradient(135deg, #3a3ad8, #7a3fd1);
    color: #fff; padding: 84px 20px 96px; text-align: center; position: relative; overflow: hidden;
}
.mb-hero h1 { font-size: clamp(32px, 6vw, 56px); margin: 0 0 14px; font-weight: 800; letter-spacing: -1px; }
.mb-hero p { max-width: 640px; margin: 0 auto 30px; font-size: 18px; opacity: .92; line-height: 1.6; }
.mb-hero-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.mb-hero .mb-btn { border-color: transparent; }
.mb-hero .mb-btn-light { background: #fff; color: var(--mb-primary-dark); }
.mb-hero .mb-btn-ghost { background: rgba(255, 255, 255, .15); color: #fff; border: 1px solid rgba(255, 255, 255, .5); }
.mb-hero .mb-btn-ghost:hover { background: rgba(255, 255, 255, .25); color: #fff; }
.mb-keys { display: flex; justify-content: center; margin-top: 46px; height: 56px; opacity: .9; }
.mb-keys i { width: 34px; background: #fff; border: 1px solid #c9c9e6; border-radius: 0 0 6px 6px; position: relative; }
.mb-keys i.b { background: #1e2235; width: 22px; height: 34px; margin: 0 -11px; z-index: 1; border-radius: 0 0 4px 4px; border: 0; }

.mb-section { padding: 52px 0 8px; }
.mb-section h2 { font-size: 26px; margin: 0 0 6px; }
.mb-section .mb-sub { color: var(--mb-muted); margin: 0 0 24px; }
.mb-section-head { display: flex; align-items: flex-end; justify-content: space-between; gap: 12px; margin-bottom: 22px; flex-wrap: wrap; }
.mb-section-head .mb-sub { margin: 0; }

.mb-features { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 18px; }
.mb-feature { background: var(--mb-surface); border: 1px solid var(--mb-border); border-radius: var(--mb-radius); padding: 24px; box-shadow: var(--mb-shadow); }
.mb-feature .ico { font-size: 30px; margin-bottom: 10px; }
.mb-feature h3 { margin: 0 0 6px; font-size: 17px; }
.mb-feature p { margin: 0; color: var(--mb-muted); font-size: 14px; line-height: 1.55; }

/* ---------- Danh sách bản nhạc ---------- */
.mb-songs { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 16px; }
.mb-song {
    background: var(--mb-surface); border: 1px solid var(--mb-border); border-radius: var(--mb-radius);
    padding: 18px; box-shadow: var(--mb-shadow); display: flex; flex-direction: column; gap: 12px;
    transition: transform .15s, border-color .15s;
}
.mb-song:hover { transform: translateY(-2px); border-color: var(--mb-primary); }
.mb-song-top { display: flex; gap: 12px; align-items: center; }
.mb-song-ico { width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; font-size: 22px; background: #eef0ff; flex: none; }
.mb-song-title { font-weight: 700; word-break: break-word; }
.mb-song-meta { color: var(--mb-muted); font-size: 12.5px; margin-top: 2px; }
.mb-song-actions { display: flex; gap: 8px; }
.mb-song-actions .mb-btn { flex: 1; }
.mb-empty, .mb-note {
    text-align: center; color: var(--mb-muted); padding: 36px 20px; background: var(--mb-surface);
    border: 1px dashed var(--mb-border); border-radius: var(--mb-radius);
}
.mb-error { color: var(--mb-danger); font-size: 14px; margin-top: 8px; }
.mb-page-head { padding: 36px 0 0; }
.mb-page-head h1 { margin: 0 0 6px; font-size: 30px; }

.mb-footer { text-align: center; color: var(--mb-muted); font-size: 13px; padding: 48px 20px 28px; }

/* ---------- Hộp thoại đăng nhập / đăng ký ---------- */
.mb-modal { position: fixed; inset: 0; z-index: 100; background: rgba(20, 22, 50, .55); display: grid; place-items: center; padding: 16px; }
.mb-dialog { width: 100%; max-width: 410px; background: var(--mb-surface); border-radius: 18px; padding: 28px; box-shadow: 0 20px 60px rgba(0, 0, 0, .3); position: relative; font-family: "Segoe UI", system-ui, sans-serif; color: var(--mb-text); }
.mb-close { position: absolute; top: 12px; right: 14px; border: 0; background: none; font-size: 24px; color: var(--mb-muted); cursor: pointer; }
.mb-tabs { display: flex; background: var(--mb-bg); border-radius: 10px; padding: 4px; margin-bottom: 20px; }
.mb-tab { flex: 1; border: 0; background: none; padding: 9px; border-radius: 8px; font: 700 14px "Segoe UI", system-ui, sans-serif; color: var(--mb-muted); cursor: pointer; }
.mb-tab.active { background: var(--mb-surface); color: var(--mb-primary); box-shadow: 0 1px 4px rgba(0, 0, 0, .1); }
.mb-field { display: block; margin-bottom: 14px; }
.mb-field span { display: block; font-size: 13px; font-weight: 600; margin-bottom: 5px; }
.mb-field input {
    width: 100%; box-sizing: border-box; padding: 11px 12px; border: 1px solid var(--mb-border);
    border-radius: 10px; font: 15px "Segoe UI", system-ui, sans-serif; outline: none; background: #fff; color: var(--mb-text);
}
.mb-field input:focus { border-color: var(--mb-primary); box-shadow: 0 0 0 3px rgba(91, 91, 240, .15); }
.mb-dialog .mb-btn-primary { width: 100%; padding: 12px; }

@media (max-width: 640px) {
    .mb-nav { padding: 0 14px; gap: 10px; }
    .mb-user .mb-uname { display: none; }
    .mb-hero { padding: 56px 16px 64px; }
}