/* =============================================================
   LỚP HỌC ONLINE — giao diện
   Muốn đổi màu chủ đạo: sửa --brand ở dưới (hoặc đổi trong
   trang Quản trị → Cài đặt, web sẽ tự áp dụng).
   ============================================================= */

:root {
  --brand: #4f46e5;
  --brand-600: #4338ca;
  --brand-soft: rgba(79, 70, 229, 0.10);
  --brand-ring: rgba(79, 70, 229, 0.28);

  --bg: #f6f7fb;
  --bg-elev: #ffffff;
  --bg-sunk: #eef0f6;
  --line: #e4e7ee;
  --line-strong: #d3d8e3;
  --text: #10131c;
  --text-soft: #5b6478;
  --text-mute: #8b93a6;

  --ok: #16a34a;
  --ok-soft: rgba(22, 163, 74, 0.12);
  --warn: #d97706;
  --warn-soft: rgba(217, 119, 6, 0.12);
  --bad: #dc2626;
  --bad-soft: rgba(220, 38, 38, 0.12);

  --r-sm: 8px;
  --r: 12px;
  --r-lg: 16px;
  --r-xl: 22px;
  --shadow-1: 0 1px 2px rgba(16, 19, 28, 0.05), 0 1px 3px rgba(16, 19, 28, 0.06);
  --shadow-2: 0 4px 12px rgba(16, 19, 28, 0.07), 0 2px 4px rgba(16, 19, 28, 0.04);
  --shadow-3: 0 18px 40px rgba(16, 19, 28, 0.14);
  --header-h: 62px;
  --font: 'Be Vietnam Pro', system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}

[data-theme='dark'] {
  --bg: #0e1117;
  --bg-elev: #161a23;
  --bg-sunk: #1d222d;
  --line: #262c38;
  --line-strong: #333b4a;
  --text: #eef1f7;
  --text-soft: #a7b0c2;
  --text-mute: #7b8598;
  --brand-soft: rgba(129, 140, 248, 0.16);
  --shadow-1: 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow-2: 0 6px 18px rgba(0, 0, 0, 0.45);
  --shadow-3: 0 22px 48px rgba(0, 0, 0, 0.6);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  font-size: 15px;
  line-height: 1.55;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
button, input, select, textarea { font: inherit; color: inherit; }
h1, h2, h3, h4 { margin: 0; line-height: 1.25; font-weight: 700; letter-spacing: -0.01em; }
p { margin: 0 0 .7em; }
::selection { background: var(--brand-ring); }

/* ---------- Màn hình chờ ---------- */
.boot { min-height: 100vh; display: grid; place-content: center; justify-items: center; gap: 18px; }
.boot-logo { font-size: 44px; }
.spinner {
  width: 26px; height: 26px; border-radius: 50%;
  border: 3px solid var(--line-strong); border-top-color: var(--brand);
  animation: spin .7s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* =============================================================
   NÚT BẤM
   ============================================================= */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 9px 16px; border-radius: var(--r); border: 1px solid transparent;
  background: var(--bg-sunk); color: var(--text); font-weight: 600; font-size: 14px;
  cursor: pointer; transition: .16s ease; white-space: nowrap; text-align: center;
}
.btn:hover { transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn:focus-visible { outline: 3px solid var(--brand-ring); outline-offset: 2px; }
.btn[disabled] { opacity: .55; pointer-events: none; }
.btn-primary { background: var(--brand); color: #fff; box-shadow: 0 2px 10px var(--brand-ring); }
.btn-primary:hover { background: var(--brand-600); }
.btn-ghost { background: transparent; border-color: var(--line); }
.btn-ghost:hover { background: var(--bg-sunk); }
.btn-danger { background: var(--bad-soft); color: var(--bad); }
.btn-danger:hover { background: var(--bad); color: #fff; }
.btn-sm { padding: 6px 11px; font-size: 13px; border-radius: var(--r-sm); }
.btn-lg { padding: 13px 24px; font-size: 15.5px; border-radius: var(--r-lg); }
.btn-block { width: 100%; }
.btn-icon { padding: 8px; width: 36px; height: 36px; border-radius: 10px; }

/* =============================================================
   Ô NHẬP LIỆU
   ============================================================= */
.field { display: block; margin-bottom: 14px; }
.field > .label { display: block; font-size: 13px; font-weight: 600; color: var(--text-soft); margin-bottom: 6px; }
.field .hint { font-size: 12.5px; color: var(--text-mute); margin-top: 5px; }
.input, .select, .textarea {
  width: 100%; padding: 10px 13px; border-radius: var(--r);
  border: 1.5px solid var(--line); background: var(--bg-elev); color: var(--text);
  transition: border-color .15s, box-shadow .15s; font-size: 14.5px;
}
.input:focus, .select:focus, .textarea:focus {
  outline: none; border-color: var(--brand); box-shadow: 0 0 0 4px var(--brand-ring);
}
.textarea { min-height: 96px; resize: vertical; line-height: 1.6; }
.select { appearance: none; background-image: url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%238b93a6' stroke-width='2.5' stroke-linecap='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 11px center; background-size: 16px; padding-right: 34px; }
.check { display: flex; align-items: flex-start; gap: 10px; cursor: pointer; padding: 9px 11px; border-radius: var(--r); border: 1.5px solid var(--line); background: var(--bg-elev); margin-bottom: 9px; }
.check:hover { border-color: var(--line-strong); }
.check input { margin-top: 3px; width: 17px; height: 17px; accent-color: var(--brand); flex: none; }
.check .t { font-size: 14px; font-weight: 600; }
.check .d { font-size: 12.5px; color: var(--text-mute); font-weight: 400; }
.row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 560px) { .row { grid-template-columns: 1fr; } }

/* =============================================================
   THẺ / KHỐI
   ============================================================= */
.card { background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r-lg); box-shadow: var(--shadow-1); }
.card-pad { padding: 18px; }
.section-title { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin: 26px 0 14px; }
.section-title h2 { font-size: 19px; }
.muted { color: var(--text-mute); }
.soft { color: var(--text-soft); }
.small { font-size: 13px; }
.stack { display: flex; flex-direction: column; gap: 12px; }
.hstack { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.spacer { flex: 1; }

.badge { display: inline-flex; align-items: center; gap: 5px; padding: 3px 9px; border-radius: 999px; font-size: 12px; font-weight: 600; background: var(--bg-sunk); color: var(--text-soft); }
.badge-brand { background: var(--brand-soft); color: var(--brand); }
.badge-ok { background: var(--ok-soft); color: var(--ok); }
.badge-warn { background: var(--warn-soft); color: var(--warn); }
.badge-bad { background: var(--bad-soft); color: var(--bad); }

.progress { height: 7px; border-radius: 999px; background: var(--bg-sunk); overflow: hidden; }
.progress > i { display: block; height: 100%; border-radius: 999px; background: linear-gradient(90deg, var(--brand), #22c55e); transition: width .4s ease; }

.empty { text-align: center; padding: 46px 20px; color: var(--text-mute); }
.empty .ico { font-size: 40px; margin-bottom: 10px; }
.empty h3 { color: var(--text); margin-bottom: 6px; font-size: 17px; }

/* =============================================================
   THANH TRÊN CÙNG
   ============================================================= */
.topbar {
  position: sticky; top: 0; z-index: 40; height: var(--header-h);
  display: flex; align-items: center; gap: 14px; padding: 0 18px;
  background: color-mix(in srgb, var(--bg-elev) 88%, transparent);
  backdrop-filter: saturate(160%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 16.5px; letter-spacing: -.02em; }
.brand .mark { width: 32px; height: 32px; border-radius: 9px; display: grid; place-content: center; background: var(--brand); color: #fff; font-size: 17px; }
.nav { display: flex; gap: 3px; margin-left: 10px; }
.nav a { padding: 8px 13px; border-radius: 10px; font-weight: 600; font-size: 14px; color: var(--text-soft); }
.nav a:hover { background: var(--bg-sunk); color: var(--text); }
.nav a.on { background: var(--brand-soft); color: var(--brand); }
.avatar { width: 34px; height: 34px; border-radius: 50%; background: var(--brand); color: #fff; display: grid; place-content: center; font-weight: 700; font-size: 14px; flex: none; }
.usermenu { position: relative; }
.usermenu .panel {
  position: absolute; right: 0; top: calc(100% + 8px); width: 232px; padding: 7px;
  background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r-lg); box-shadow: var(--shadow-3); z-index: 60;
}
.usermenu .panel button, .usermenu .panel a {
  display: flex; align-items: center; gap: 9px; width: 100%; padding: 9px 11px; border: 0; border-radius: 9px;
  background: transparent; cursor: pointer; font-size: 14px; font-weight: 500; text-align: left;
}
.usermenu .panel button:hover, .usermenu .panel a:hover { background: var(--bg-sunk); }
.usermenu .head { padding: 10px 11px 12px; border-bottom: 1px solid var(--line); margin-bottom: 6px; }

.page { max-width: 1180px; margin: 0 auto; padding: 22px 18px 70px; }
.page-wide { max-width: 1500px; }

/* =============================================================
   TRANG ĐĂNG NHẬP
   ============================================================= */
.auth-wrap { min-height: 100vh; display: grid; grid-template-columns: 1.05fr .95fr; }
.auth-side {
  background: linear-gradient(150deg, var(--brand), #7c3aed 55%, #0ea5e9);
  color: #fff; padding: 54px; display: flex; flex-direction: column; justify-content: center; gap: 20px; position: relative; overflow: hidden;
}
.auth-side::after { content: ''; position: absolute; inset: 0; background: radial-gradient(700px 380px at 78% 12%, rgba(255,255,255,.22), transparent 62%); }
.auth-side > * { position: relative; z-index: 1; }
.auth-side h1 { font-size: 38px; line-height: 1.15; letter-spacing: -.03em; }
.auth-side p { font-size: 16px; opacity: .93; max-width: 460px; }
.auth-points { display: grid; gap: 12px; margin-top: 8px; }
.auth-points div { display: flex; gap: 11px; align-items: flex-start; font-size: 14.5px; opacity: .96; }
.auth-points span { flex: none; width: 26px; height: 26px; border-radius: 8px; background: rgba(255,255,255,.2); display: grid; place-content: center; }
.auth-main { display: grid; place-content: center; padding: 40px 26px; }
.auth-box { width: min(410px, 92vw); }
.auth-box h2 { font-size: 25px; margin-bottom: 5px; }
.auth-tabs { display: flex; gap: 4px; background: var(--bg-sunk); padding: 4px; border-radius: var(--r); margin: 20px 0 18px; }
.auth-tabs button { flex: 1; padding: 8px; border: 0; background: transparent; border-radius: 9px; cursor: pointer; font-weight: 600; font-size: 14px; color: var(--text-soft); }
.auth-tabs button.on { background: var(--bg-elev); color: var(--text); box-shadow: var(--shadow-1); }
@media (max-width: 900px) { .auth-wrap { grid-template-columns: 1fr; } .auth-side { padding: 34px 24px; } .auth-side h1 { font-size: 27px; } .auth-points { display: none; } }

/* =============================================================
   DANH SÁCH KHOÁ HỌC
   ============================================================= */
.hero {
  background: linear-gradient(130deg, var(--brand), #7c3aed 60%, #0ea5e9);
  color: #fff; border-radius: var(--r-xl); padding: 30px 32px; margin-bottom: 8px;
  display: flex; gap: 24px; align-items: center; flex-wrap: wrap; box-shadow: var(--shadow-2);
}
.hero h1 { font-size: 26px; letter-spacing: -.02em; }
.hero p { opacity: .92; margin: 6px 0 0; max-width: 620px; }
.hero .stats { display: flex; gap: 10px; margin-left: auto; flex-wrap: wrap; }
.hero .stat { background: rgba(255,255,255,.16); border-radius: var(--r); padding: 11px 17px; min-width: 96px; }
.hero .stat b { display: block; font-size: 22px; line-height: 1.2; }
.hero .stat span { font-size: 12.5px; opacity: .9; }

.chips { display: flex; gap: 8px; overflow-x: auto; padding: 4px 0 6px; scrollbar-width: thin; }
.chip { padding: 8px 15px; border-radius: 999px; border: 1.5px solid var(--line); background: var(--bg-elev); cursor: pointer; font-weight: 600; font-size: 13.5px; white-space: nowrap; transition: .15s; }
.chip:hover { border-color: var(--line-strong); }
.chip.on { background: var(--brand); border-color: var(--brand); color: #fff; }

.grid-courses { display: grid; grid-template-columns: repeat(auto-fill, minmax(276px, 1fr)); gap: 18px; }
.course-card { background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden; cursor: pointer; transition: .2s; display: flex; flex-direction: column; box-shadow: var(--shadow-1); }
.course-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-2); border-color: var(--line-strong); }
.course-thumb { aspect-ratio: 16/9; background: var(--bg-sunk); position: relative; display: grid; place-content: center; font-size: 56px; opacity: 1; }
.course-thumb > span { filter: saturate(.9); opacity: .55; }
.course-thumb img { width: 100%; height: 100%; object-fit: cover; }
.course-thumb .lock { position: absolute; inset: 0; background: rgba(4,7,15,.5); color: #fff; display: grid; place-content: center; font-size: 26px; backdrop-filter: blur(2px); }
.course-body { padding: 15px 16px 17px; display: flex; flex-direction: column; gap: 8px; flex: 1; }
.course-body h3 { font-size: 16px; }
.course-meta { display: flex; gap: 12px; font-size: 12.5px; color: var(--text-mute); margin-top: auto; padding-top: 4px; }

/* =============================================================
   TRANG KHOÁ HỌC + DANH SÁCH BÀI
   ============================================================= */
.course-head { display: grid; grid-template-columns: 1.6fr 1fr; gap: 26px; align-items: start; margin-bottom: 8px; }
@media (max-width: 860px) { .course-head { grid-template-columns: 1fr; } }
.curriculum { display: flex; flex-direction: column; gap: 12px; }
.sec { border: 1px solid var(--line); border-radius: var(--r-lg); overflow: hidden; background: var(--bg-elev); }
.sec > header { padding: 13px 16px; background: var(--bg-sunk); font-weight: 700; display: flex; justify-content: space-between; gap: 10px; align-items: center; cursor: pointer; font-size: 14.5px; }
.lesson-row { display: flex; align-items: center; gap: 12px; padding: 12px 16px; border-top: 1px solid var(--line); cursor: pointer; transition: background .13s; }
.lesson-row:hover { background: var(--bg-sunk); }
.lesson-row .ico { width: 30px; height: 30px; border-radius: 50%; display: grid; place-content: center; background: var(--bg-sunk); font-size: 13px; flex: none; }
.lesson-row.done .ico { background: var(--ok-soft); color: var(--ok); }
.lesson-row.locked { opacity: .62; }
.lesson-row .t { flex: 1; min-width: 0; }
.lesson-row .t b { display: block; font-weight: 600; font-size: 14.5px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.lesson-row .t span { font-size: 12.5px; color: var(--text-mute); }

/* =============================================================
   TRÌNH PHÁT VIDEO
   ============================================================= */
.player-layout { display: grid; grid-template-columns: minmax(0, 1fr) 340px; gap: 22px; align-items: start; }
@media (max-width: 1050px) { .player-layout { grid-template-columns: 1fr; } }
.video-shell { position: relative; background: #000; border-radius: var(--r-lg); overflow: hidden; aspect-ratio: 16/9; box-shadow: var(--shadow-2); }
.video-shell video, .video-shell iframe { width: 100%; height: 100%; display: block; border: 0; background: #000; }
.video-shell .novideo { position: absolute; inset: 0; display: grid; place-content: center; justify-items: center; gap: 10px; color: #cbd5e1; text-align: center; padding: 20px; }
.watermark { position: absolute; color: rgba(255,255,255,.32); font-size: 12.5px; font-weight: 600; pointer-events: none; text-shadow: 0 1px 3px rgba(0,0,0,.6); transition: left 1.4s linear, top 1.4s linear; z-index: 5; }
.playlist { max-height: 74vh; overflow: auto; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--bg-elev); }
.playlist .p-head { padding: 13px 16px; border-bottom: 1px solid var(--line); font-weight: 700; position: sticky; top: 0; background: var(--bg-elev); z-index: 2; }
.playlist .lesson-row.on { background: var(--brand-soft); }
.playlist .lesson-row.on .t b { color: var(--brand); }

.tabs { display: flex; gap: 3px; border-bottom: 1.5px solid var(--line); margin: 22px 0 16px; overflow-x: auto; }
.tabs button { padding: 10px 15px; border: 0; background: transparent; cursor: pointer; font-weight: 600; font-size: 14px; color: var(--text-soft); border-bottom: 2.5px solid transparent; margin-bottom: -1.5px; white-space: nowrap; }
.tabs button.on { color: var(--brand); border-color: var(--brand); }

.att { display: flex; align-items: center; gap: 12px; padding: 11px 14px; border: 1px solid var(--line); border-radius: var(--r); margin-bottom: 9px; background: var(--bg-elev); }
.att .fi { width: 34px; height: 34px; border-radius: 9px; background: var(--brand-soft); color: var(--brand); display: grid; place-content: center; font-size: 15px; flex: none; }

/* Quiz */
.quiz-q { border: 1px solid var(--line); border-radius: var(--r-lg); padding: 16px; margin-bottom: 13px; background: var(--bg-elev); }
.quiz-q > b { display: block; margin-bottom: 11px; font-size: 15px; }
.opt { display: flex; align-items: flex-start; gap: 10px; padding: 10px 13px; border: 1.5px solid var(--line); border-radius: var(--r); margin-bottom: 8px; cursor: pointer; transition: .13s; }
.opt:hover { border-color: var(--brand); }
.opt input { margin-top: 3px; accent-color: var(--brand); width: 17px; height: 17px; }
.opt.right { border-color: var(--ok); background: var(--ok-soft); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.explain { font-size: 13.5px; color: var(--text-soft); background: var(--bg-sunk); border-radius: var(--r-sm); padding: 10px 12px; margin-top: 8px; }

/* =============================================================
   TRANG QUẢN TRỊ
   ============================================================= */
.admin-layout { display: grid; grid-template-columns: 226px minmax(0, 1fr); gap: 22px; align-items: start; }
@media (max-width: 900px) { .admin-layout { grid-template-columns: 1fr; } }
.admin-nav { position: sticky; top: calc(var(--header-h) + 16px); display: flex; flex-direction: column; gap: 3px; }
.admin-nav button { display: flex; align-items: center; gap: 10px; padding: 10px 13px; border: 0; background: transparent; border-radius: var(--r); cursor: pointer; font-weight: 600; font-size: 14px; color: var(--text-soft); text-align: left; }
.admin-nav button:hover { background: var(--bg-sunk); color: var(--text); }
.admin-nav button.on { background: var(--brand); color: #fff; }
@media (max-width: 900px) { .admin-nav { flex-direction: row; overflow-x: auto; position: static; padding-bottom: 6px; } }

.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(168px, 1fr)); gap: 13px; }
.stat-box { background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 16px; }
.stat-box b { display: block; font-size: 26px; letter-spacing: -.02em; }
.stat-box span { font-size: 13px; color: var(--text-mute); }
.stat-box .ico { font-size: 18px; margin-bottom: 6px; }

.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--r-lg); background: var(--bg-elev); }
table.tbl { width: 100%; border-collapse: collapse; font-size: 14px; min-width: 560px; }
table.tbl th { text-align: left; padding: 12px 14px; background: var(--bg-sunk); font-size: 12.5px; text-transform: uppercase; letter-spacing: .04em; color: var(--text-mute); font-weight: 700; white-space: nowrap; }
table.tbl td { padding: 12px 14px; border-top: 1px solid var(--line); vertical-align: middle; }
table.tbl tr:hover td { background: var(--bg-sunk); }

.drop {
  border: 2.5px dashed var(--line-strong); border-radius: var(--r-lg); padding: 30px 20px; text-align: center;
  cursor: pointer; transition: .16s; background: var(--bg-sunk);
}
.drop:hover, .drop.over { border-color: var(--brand); background: var(--brand-soft); }
.drop .ico { font-size: 32px; margin-bottom: 8px; }
.upbar { margin-top: 12px; }
.upbar .progress { height: 10px; }
.upbar .txt { display: flex; justify-content: space-between; font-size: 13px; color: var(--text-soft); margin-top: 7px; }

.sortable-item { display: flex; align-items: center; gap: 10px; padding: 10px 13px; border: 1px solid var(--line); border-radius: var(--r); background: var(--bg-elev); margin-bottom: 8px; }
.sortable-item .grab { cursor: grab; color: var(--text-mute); user-select: none; }
.sortable-item.dragging { opacity: .45; }

/* =============================================================
   HỘP THOẠI & THÔNG BÁO
   ============================================================= */
.modal-back { position: fixed; inset: 0; background: rgba(8, 11, 20, .55); backdrop-filter: blur(3px); z-index: 100; display: grid; place-items: center; padding: 18px; animation: fade .16s ease; }
@keyframes fade { from { opacity: 0 } }
.modal { width: min(620px, 100%); max-height: 88vh; overflow: auto; background: var(--bg-elev); border-radius: var(--r-xl); box-shadow: var(--shadow-3); animation: pop .18s ease; }
.modal.wide { width: min(880px, 100%); }
@keyframes pop { from { transform: translateY(14px) scale(.985); opacity: 0 } }
.modal > header { padding: 18px 22px; border-bottom: 1px solid var(--line); display: flex; align-items: center; justify-content: space-between; gap: 12px; position: sticky; top: 0; background: var(--bg-elev); z-index: 2; }
.modal > header h3 { font-size: 17.5px; }
.modal > .body { padding: 20px 22px; }
.modal > footer { padding: 15px 22px; border-top: 1px solid var(--line); display: flex; gap: 10px; justify-content: flex-end; position: sticky; bottom: 0; background: var(--bg-elev); }

.toasts { position: fixed; right: 18px; bottom: 18px; z-index: 200; display: flex; flex-direction: column; gap: 9px; max-width: min(380px, 92vw); }
.toast { background: var(--bg-elev); border: 1px solid var(--line); border-left: 4px solid var(--brand); border-radius: var(--r); padding: 12px 15px; box-shadow: var(--shadow-3); font-size: 14px; animation: slide .2s ease; }
.toast.ok { border-left-color: var(--ok); }
.toast.err { border-left-color: var(--bad); }
@keyframes slide { from { transform: translateX(20px); opacity: 0 } }

.skeleton { background: linear-gradient(90deg, var(--bg-sunk) 25%, var(--line) 37%, var(--bg-sunk) 63%); background-size: 400% 100%; animation: sk 1.3s ease infinite; border-radius: var(--r); }
@keyframes sk { 0% { background-position: 100% 50% } 100% { background-position: 0 50% } }

.notice { padding: 13px 16px; border-radius: var(--r); background: var(--warn-soft); color: var(--warn); font-size: 14px; font-weight: 500; margin-bottom: 16px; display: flex; gap: 10px; align-items: flex-start; }
.notice.info { background: var(--brand-soft); color: var(--brand); }

.prose { line-height: 1.75; color: var(--text-soft); }
.prose h3 { color: var(--text); margin: 18px 0 8px; font-size: 16px; }
.prose ul { padding-left: 20px; }
.prose code { background: var(--bg-sunk); padding: 2px 6px; border-radius: 6px; font-size: 13px; }

@media print { .topbar, .btn, .tabs { display: none !important; } }

/* ---------- Tiện ích nhỏ ---------- */
@media (max-width: 620px) {
  .hide-sm { display: none; }
  .nav a { padding: 8px 10px; font-size: 13.5px; }
  .page { padding: 16px 13px 60px; }
  .hero { padding: 22px 20px; border-radius: 18px; }
  .hero h1 { font-size: 21px; }
  .hero .stats { margin-left: 0; }
  .modal > .body { padding: 16px; }
  .modal > header, .modal > footer { padding: 14px 16px; }
}
.grab { user-select: none; }
input[type='color'] { cursor: pointer; }

/* =============================================================
   THI THỬ & BÀI TẬP — màn hình làm bài
   ============================================================= */
body.exam-mode { overflow: hidden; }
.exam-wrap { position: fixed; inset: 0; display: flex; flex-direction: column; background: var(--bg); z-index: 50; }
.no-select { user-select: none; -webkit-user-select: none; }
.no-select input, .no-select textarea { user-select: text; -webkit-user-select: text; }

.exam-top {
  display: flex; align-items: center; gap: 16px; padding: 10px 18px;
  background: var(--bg-elev); border-bottom: 1px solid var(--line); box-shadow: var(--shadow-1); flex: none;
}
.exam-top > div:first-child { flex: 1; min-width: 0; }
.exam-clock {
  font-variant-numeric: tabular-nums; font-weight: 800; font-size: 26px; letter-spacing: -.02em;
  padding: 4px 16px; border-radius: 12px; background: var(--bg-sunk); color: var(--text);
}
.exam-clock.warn { background: var(--warn-soft); color: var(--warn); }
.exam-clock.danger { background: var(--bad-soft); color: var(--bad); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: .55; } }
.exam-warn { font-size: 13px; font-weight: 600; color: var(--bad); background: var(--bad-soft); padding: 5px 11px; border-radius: 999px; }

.exam-body { flex: 1; display: grid; grid-template-columns: minmax(0, 1fr) 262px; gap: 18px; overflow: hidden; padding: 18px; }
.exam-main { overflow-y: auto; padding-right: 6px; }
.exam-side { overflow-y: auto; }
@media (max-width: 900px) {
  .exam-body { grid-template-columns: 1fr; padding: 12px; }
  .exam-side { display: none; }
  .exam-clock { font-size: 21px; padding: 3px 11px; }
}

.exam-part { font-size: 13px; font-weight: 700; color: var(--brand); background: var(--brand-soft); padding: 8px 14px; border-radius: 10px; margin-bottom: 14px; }
.exam-q { background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r-lg); padding: 20px 22px; box-shadow: var(--shadow-1); }
.exam-qno { font-weight: 800; font-size: 16px; background: var(--brand); color: #fff; padding: 3px 12px; border-radius: 999px; }
.exam-qno.ok { background: var(--ok); }
.exam-qno.bad { background: var(--bad); }
.exam-content { font-size: 16.5px; line-height: 1.75; }
.exam-content img.tikz-fig { max-width: 100%; margin: 12px auto; display: block; }
[data-theme='dark'] .exam-content img.tikz-fig { filter: invert(1) hue-rotate(180deg); }
.tikz-fail { color: var(--bad); font-size: 13px; font-style: italic; }

.exam-opt {
  display: flex; align-items: flex-start; gap: 12px; padding: 12px 15px; margin-bottom: 9px;
  border: 1.5px solid var(--line); border-radius: var(--r); cursor: pointer; transition: .13s; background: var(--bg-elev);
}
.exam-opt:hover { border-color: var(--brand); background: var(--brand-soft); }
.exam-opt.on { border-color: var(--brand); background: var(--brand-soft); box-shadow: 0 0 0 3px var(--brand-ring); }
.exam-opt.right { border-color: var(--ok); background: var(--ok-soft); }
.exam-opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.exam-opt .ltr { flex: none; width: 27px; height: 27px; border-radius: 50%; background: var(--bg-sunk); display: grid; place-content: center; font-weight: 700; font-size: 13px; }
.exam-opt.on .ltr { background: var(--brand); color: #fff; }
.exam-opt.right .ltr { background: var(--ok); color: #fff; }
.exam-opt.wrong .ltr { background: var(--bad); color: #fff; }
.exam-opt-t { flex: 1; min-width: 0; }

.tf-table { width: 100%; border-collapse: collapse; }
.tf-table th { text-align: left; padding: 8px 10px; font-size: 12px; text-transform: uppercase; letter-spacing: .04em; color: var(--text-mute); background: var(--bg-sunk); }
.tf-table td { padding: 11px 10px; border-top: 1px solid var(--line); vertical-align: top; }
.tf-ltr { font-weight: 700; color: var(--text-soft); width: 34px; }
.tf-pick { text-align: center; }
.tf-btn {
  display: inline-grid; place-content: center; width: 44px; height: 36px; border-radius: 10px;
  border: 1.5px solid var(--line); font-weight: 700; cursor: pointer; transition: .13s; user-select: none;
}
.tf-btn:hover { border-color: var(--brand); }
.tf-btn.on-t { background: var(--ok); border-color: var(--ok); color: #fff; }
.tf-btn.on-f { background: var(--bad); border-color: var(--bad); color: #fff; }

.short-box { max-width: 340px; }
.short-input { font-size: 21px; font-weight: 700; text-align: center; letter-spacing: .02em; }

.exam-nav { display: flex; align-items: center; gap: 10px; margin-top: 16px; padding-bottom: 20px; }

.qmap { display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; }
.qmap-h { grid-column: 1/-1; font-size: 11.5px; font-weight: 700; color: var(--text-mute); text-transform: uppercase; letter-spacing: .05em; margin: 6px 0 2px; }
.qmap-b {
  aspect-ratio: 1; border: 1.5px solid var(--line); border-radius: 9px; background: var(--bg-elev);
  cursor: pointer; font-weight: 700; font-size: 13px; transition: .12s;
}
.qmap-b:hover { border-color: var(--brand); }
.qmap-b.done { background: var(--ok-soft); border-color: var(--ok); color: var(--ok); }
.qmap-b.cur { box-shadow: 0 0 0 3px var(--brand-ring); border-color: var(--brand); }
.dot { display: inline-block; width: 11px; height: 11px; border-radius: 3px; border: 1.5px solid var(--line); vertical-align: -1px; }
.dot.done { background: var(--ok-soft); border-color: var(--ok); }

.exam-wm { position: fixed; color: rgba(120,130,150,.28); font-size: 13px; font-weight: 700; pointer-events: none; z-index: 60; transition: left 1.5s linear, top 1.5s linear; }

.vio-overlay { position: fixed; inset: 0; background: rgba(8,11,20,.72); backdrop-filter: blur(5px); z-index: 300; display: grid; place-items: center; padding: 20px; }
.vio-box { background: var(--bg-elev); border-radius: var(--r-xl); padding: 32px 30px; text-align: center; max-width: 460px; box-shadow: var(--shadow-3); }
.vio-box h2 { font-size: 20px; margin: 10px 0 8px; }
.vio-box p { color: var(--text-soft); font-size: 14.5px; }
.vio-box .btn { margin-top: 14px; }

/* Bảng soạn đề của giáo viên */
.qedit { border: 1px solid var(--line); border-radius: var(--r-lg); padding: 15px 16px; margin-bottom: 12px; background: var(--bg-elev); }
.qedit textarea { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 13.5px; }
.qedit .qtype { font-size: 11.5px; font-weight: 700; text-transform: uppercase; letter-spacing: .05em; padding: 3px 9px; border-radius: 999px; }
.latex-box { font-family: ui-monospace, Menlo, Consolas, monospace; font-size: 13px; min-height: 260px; }
.katex { font-size: 1.03em; }
.katex-display { margin: .6em 0; }

/* ---------- Thẻ mục kiến thức & kho tài liệu ---------- */
.grid-cats { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 14px; }
.cat-card {
  display: flex; align-items: center; gap: 14px; padding: 16px 18px; cursor: pointer;
  background: var(--bg-elev); border: 1px solid var(--line); border-left: 4px solid var(--c, var(--brand));
  border-radius: var(--r-lg); box-shadow: var(--shadow-1); transition: .18s;
}
.cat-card:hover { transform: translateY(-2px); box-shadow: var(--shadow-2); border-color: var(--c, var(--brand)); border-left-color: var(--c, var(--brand)); }
.cat-card h3 { font-size: 16px; }
.cat-ico { flex: none; width: 48px; height: 48px; border-radius: 13px; display: grid; place-content: center; font-size: 24px; }
.cat-go { font-size: 26px; color: var(--text-mute); font-weight: 300; }

.doc-row {
  display: flex; align-items: center; gap: 14px; padding: 13px 16px;
  background: var(--bg-elev); border: 1px solid var(--line); border-radius: var(--r); transition: .13s;
}
.doc-row:hover { border-color: var(--line-strong); }
.doc-ico { flex: none; width: 42px; height: 42px; border-radius: 11px; background: var(--brand-soft); display: grid; place-content: center; font-size: 20px; }

/* ===================== THỜI KHOÁ BIỂU ===================== */
.tkb-row {
  display: flex; gap: 14px; align-items: flex-start;
  padding: 13px 16px; border-top: 1px solid var(--line);
  transition: background .13s;
}
.tkb-row:first-of-type { border-top: 0; }
.tkb-row:hover { background: var(--bg-sunk); }
.tkb-row.qua { opacity: .55; }
.tkb-row.nay { background: var(--brand-soft); }
.tkb-row.nay:hover { background: var(--brand-soft); }

.tkb-when {
  flex: none; width: 62px; text-align: center; line-height: 1.25;
  display: flex; flex-direction: column; align-items: center; gap: 3px;
}
.tkb-when b {
  display: grid; place-content: center;
  width: 27px; height: 27px; border-radius: 50%;
  background: var(--bg-sunk); border: 1px solid var(--line);
  font-size: 12.5px; font-weight: 700;
}
.tkb-row.nay .tkb-when b { background: var(--primary); color: #fff; border-color: var(--primary); }
.tkb-when span { font-size: 11.5px; color: var(--fg-muted); font-weight: 600; }

.tkb-body { flex: 1; min-width: 0; }
.tkb-chapter {
  font-weight: 700; font-size: 13.5px; margin-bottom: 5px;
  color: var(--primary);
}
.tkb-k1 { font-size: 14px; line-height: 1.5; }
.tkb-k2 {
  margin-top: 8px; padding: 8px 11px; border-radius: 10px;
  background: color-mix(in srgb, #8b5cf6 11%, transparent);
  border-left: 3px solid #8b5cf6;
  font-size: 13px; line-height: 1.5; color: var(--fg-soft);
}
.tkb-tag {
  display: inline-block; font-size: 10.5px; font-weight: 800; letter-spacing: .04em;
  padding: 1px 6px; border-radius: 5px; margin-right: 5px;
  background: #8b5cf6; color: #fff; vertical-align: 1px;
}

@media (max-width: 640px) {
  .tkb-row { padding: 12px 12px; gap: 10px; }
  .tkb-when { width: 44px; }
}