:root {
  --bg: #f3f6fb;
  --card: #ffffff;
  --ink: #1d2433;
  --muted: #6b7486;
  --line: #e2e7f0;
  --pri: #2f7cf6;
  --pri-d: #1f5fcc;
  --pri-l: #e8f0ff;
  --ok: #16a34a;
  --ok-l: #e7f8ee;
  --bad: #dc2626;
  --bad-l: #fdecec;
  --warn: #d97706;
  --warn-l: #fff5e1;
  --r: 14px;
  --shadow: 0 2px 10px rgba(30, 50, 90, .07);
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font-family: "Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
  font-size: 16px; line-height: 1.5;
}
button, input, select, textarea { font: inherit; color: inherit; }
button { cursor: pointer; }
.wrap { max-width: 760px; margin: 0 auto; padding: 0 16px 48px; }
.muted { color: var(--muted); }
.small { font-size: 14px; }
.hidden { display: none !important; }
sup { font-size: .72em; line-height: 0; }
.ov { text-decoration: overline; }

/* ---------- thanh trên */
.topbar {
  position: sticky; top: 0; z-index: 20; background: rgba(255,255,255,.95);
  backdrop-filter: blur(6px); border-bottom: 1px solid var(--line);
}
.topbar .in { max-width: 760px; margin: 0 auto; padding: 10px 16px; display: flex; align-items: center; gap: 10px; }
.topbar .brand { font-weight: 700; flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topbar .who { font-size: 13px; color: var(--muted); text-align: right; line-height: 1.25; }
.iconbtn { border: 1px solid var(--line); background: #fff; border-radius: 10px; padding: 6px 10px; font-size: 14px; }

/* ---------- nút */
.btn {
  border: 1px solid var(--line); background: #fff; border-radius: 12px; padding: 11px 16px;
  font-weight: 600; transition: transform .05s, background .15s;
}
.btn:active { transform: scale(.98); }
.btn.primary { background: var(--pri); color: #fff; border-color: var(--pri); }
.btn.primary:hover { background: var(--pri-d); }
.btn.ghost { background: transparent; }
.btn.block { width: 100%; }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.row { display: flex; gap: 10px; flex-wrap: wrap; }
.row > .btn { flex: 1 1 140px; }

/* ---------- thẻ */
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--r); padding: 18px; box-shadow: var(--shadow); margin-top: 16px; }
h1 { font-size: 24px; margin: 20px 0 4px; }
h2 { font-size: 19px; margin: 0 0 10px; }
h3 { font-size: 16px; margin: 16px 0 8px; }

/* ---------- đăng nhập */
.hero { text-align: center; padding: 28px 0 6px; }
.hero .logo { font-size: 46px; }
.hero h1 { margin: 6px 0 2px; }
.tabs { display: flex; background: var(--pri-l); border-radius: 12px; padding: 4px; gap: 4px; }
.tabs button { flex: 1; border: 0; background: transparent; padding: 9px; border-radius: 9px; font-weight: 600; color: var(--pri-d); }
.tabs button.on { background: #fff; box-shadow: var(--shadow); }
label.f { display: block; margin-top: 12px; font-weight: 600; font-size: 14px; }
label.f input, label.f select {
  display: block; width: 100%; margin-top: 5px; padding: 11px 12px; border: 1px solid var(--line);
  border-radius: 10px; background: #fff; font-size: 16px;
}
label.f input:focus, label.f select:focus { outline: 2px solid var(--pri); border-color: transparent; }
.msg { margin-top: 12px; padding: 10px 12px; border-radius: 10px; font-size: 14px; }
.msg.err { background: var(--bad-l); color: var(--bad); }
.msg.info { background: var(--pri-l); color: var(--pri-d); }
.demo-note { background: var(--warn-l); color: #8a4b00; border-radius: 10px; padding: 10px 12px; font-size: 13px; margin-top: 14px; }
.foot { text-align: center; color: var(--muted); font-size: 12px; margin-top: 28px; }

/* ---------- lưới môn */
.subjects { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 12px; margin-top: 14px; }
.subj {
  border: 1px solid var(--line); background: #fff; border-radius: var(--r); padding: 16px 12px; text-align: left;
  box-shadow: var(--shadow); position: relative; min-height: 112px; display: flex; flex-direction: column; gap: 4px;
}
.subj .ic { font-size: 30px; }
.subj .nm { font-weight: 700; line-height: 1.25; }
.subj .st { font-size: 12px; color: var(--muted); margin-top: auto; }
.subj::before { content: ""; position: absolute; left: 0; top: 14px; bottom: 14px; width: 4px; border-radius: 0 4px 4px 0; background: var(--c, var(--pri)); }
.subj.off { opacity: .55; cursor: default; }

/* ---------- trang môn */
.back { border: 0; background: none; color: var(--pri-d); font-weight: 600; padding: 14px 0 0; }
.modes { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: 10px; }
.mode { border: 1px solid var(--line); border-radius: var(--r); background: #fff; padding: 14px; text-align: left; }
.mode b { display: block; font-size: 16px; }
.mode span { font-size: 13px; color: var(--muted); }
.mode.pri { background: var(--pri); color: #fff; border-color: var(--pri); }
.mode.pri span { color: #dbe7ff; }
.topic { display: flex; align-items: center; gap: 10px; padding: 10px 0; border-top: 1px solid var(--line); }
.topic:first-of-type { border-top: 0; }
.topic input { width: 20px; height: 20px; accent-color: var(--pri); flex: none; }
.topic .tn { flex: 1; min-width: 0; }
.topic .tn div { font-weight: 600; font-size: 15px; }
.bar { height: 7px; background: var(--line); border-radius: 9px; overflow: hidden; margin-top: 5px; }
.bar i { display: block; height: 100%; background: var(--ok); border-radius: 9px; }
.pct { font-size: 13px; color: var(--muted); width: 66px; text-align: right; flex: none; }
.selall { display: flex; gap: 8px; margin-bottom: 4px; }
.selall button { border: 0; background: var(--pri-l); color: var(--pri-d); border-radius: 8px; padding: 5px 10px; font-size: 13px; font-weight: 600; }
.hist { width: 100%; border-collapse: collapse; font-size: 14px; }
.hist td, .hist th { padding: 7px 4px; border-bottom: 1px solid var(--line); text-align: left; }

/* ---------- câu hỏi */
.progress { display: flex; align-items: center; gap: 10px; margin-top: 14px; font-size: 14px; color: var(--muted); }
.progress .bar { flex: 1; margin: 0; height: 9px; }
.progress .bar i { background: var(--pri); }
.qcard { background: #fff; border: 1px solid var(--line); border-radius: var(--r); padding: 18px; margin-top: 14px; box-shadow: var(--shadow); }
.q-head { font-size: 13px; color: var(--muted); margin-bottom: 6px; display: flex; gap: 8px; flex-wrap: wrap; }
.tag { background: var(--pri-l); color: var(--pri-d); border-radius: 6px; padding: 1px 8px; font-weight: 600; }
.tag.re { background: var(--warn-l); color: #8a4b00; }
.q-text { font-size: 17px; font-weight: 500; }
.q-fig { margin: 12px 0 4px; text-align: center; color: #24324f; }
.q-fig svg { max-width: 100%; height: auto; max-height: 220px; }
.q-body { margin-top: 14px; }
.opts { display: grid; gap: 9px; }
.opt {
  display: flex; gap: 10px; align-items: flex-start; text-align: left; width: 100%;
  border: 1.5px solid var(--line); background: #fff; border-radius: 12px; padding: 11px 12px;
}
.opt .lt { flex: none; width: 26px; height: 26px; border-radius: 8px; background: var(--pri-l); color: var(--pri-d); font-weight: 700; display: grid; place-items: center; font-size: 14px; }
.opt .ot { padding-top: 1px; }
.opt.sel { border-color: var(--pri); background: var(--pri-l); }
.opt.ok, .tf button.ok, .grp button.ok { border-color: var(--ok); background: var(--ok-l); }
.opt.ok .lt { background: var(--ok); color: #fff; }
.opt.bad, .tf button.bad, .grp button.bad { border-color: var(--bad); background: var(--bad-l); }
.opt.bad .lt { background: var(--bad); color: #fff; }
.opt:disabled, .tf button:disabled, .grp button:disabled { cursor: default; color: var(--ink); }

.tf-row, .grp-row { border: 1px solid var(--line); border-radius: 12px; padding: 10px 12px; margin-bottom: 8px; }
.tf-row { display: flex; gap: 10px; align-items: center; }
.tf-s { flex: 1; }
.tf-b { display: flex; gap: 6px; flex: none; }
.tf-b button, .grp-b button { border: 1.5px solid var(--line); background: #fff; border-radius: 10px; padding: 7px 12px; font-weight: 600; font-size: 14px; }
.tf-b button.sel, .grp-b button.sel { border-color: var(--pri); background: var(--pri); color: #fff; }
.tf-b button.sel.ok, .grp-b button.sel.ok { background: var(--ok); border-color: var(--ok); color: #fff; }
.tf-b button.sel.bad, .grp-b button.sel.bad { background: var(--bad); border-color: var(--bad); color: #fff; }
.grp-t { font-weight: 600; margin-bottom: 7px; }
.grp-b { display: flex; flex-wrap: wrap; gap: 6px; }
@media (max-width: 480px) {
  .tf-row { flex-direction: column; align-items: stretch; }
  .tf-b button { flex: 1; }
}
.short { display: flex; align-items: center; gap: 8px; }
.short input { flex: 1; max-width: 260px; padding: 12px; font-size: 18px; border: 1.5px solid var(--line); border-radius: 12px; }
.short input:focus { outline: 2px solid var(--pri); border-color: transparent; }
.short input.ok { border-color: var(--ok); background: var(--ok-l); }
.short input.bad { border-color: var(--bad); background: var(--bad-l); }
.short .unit { font-weight: 600; color: var(--muted); }
.ord-lbl { font-size: 13px; color: var(--muted); margin: 8px 0 6px; }
.ord-pool { display: flex; flex-direction: column; gap: 7px; }
.chip { border: 1.5px dashed var(--pri); background: var(--pri-l); border-radius: 10px; padding: 9px 12px; text-align: left; }
.ord-list { margin: 0; padding-left: 26px; min-height: 30px; }
.ord-it { border: 1.5px solid var(--pri); border-radius: 10px; padding: 8px 10px; margin-bottom: 6px; background: #fff; cursor: pointer; }
.ord-it.ok { border-color: var(--ok); background: var(--ok-l); cursor: default; }
.ord-it.bad { border-color: var(--bad); background: var(--bad-l); cursor: default; }
.ans-ol { margin: 4px 0 0; padding-left: 22px; }
.q-actions { margin-top: 14px; }
.q-actions .btn { min-width: 140px; }
.q-feedback { display: none; margin-top: 14px; border-radius: 12px; padding: 12px 14px; }
.q-feedback.show { display: block; }
.fb-ok { background: var(--ok-l); border: 1px solid #b6e7c8; }
.fb-bad { background: var(--bad-l); border: 1px solid #f6c3c3; }
.fb-title { font-weight: 700; margin-bottom: 4px; }
.fb-ans span { font-weight: 600; }
.fb-ex { margin-top: 6px; }
.after { display: flex; gap: 10px; align-items: center; margin-top: 12px; flex-wrap: wrap; }
.after .btn { flex: 1 1 180px; }
.report { border: 0; background: none; color: var(--muted); text-decoration: underline; font-size: 13px; }

/* ---------- kết quả */
.big { font-size: 44px; font-weight: 800; color: var(--pri-d); line-height: 1.1; }
.stat { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin-top: 12px; text-align: center; }
.stat div { background: var(--bg); border-radius: 12px; padding: 10px 4px; }
.stat b { display: block; font-size: 20px; }

/* ---------- thi thử */
.exambar { position: sticky; top: 49px; z-index: 15; background: #fff; border: 1px solid var(--line); border-radius: 12px; margin-top: 12px; padding: 8px 12px; display: flex; align-items: center; gap: 10px; box-shadow: var(--shadow); }
.exambar .tm { font-weight: 700; font-variant-numeric: tabular-nums; }
.exambar .tm.low { color: var(--bad); }
.part-title { font-weight: 700; margin: 22px 0 0; color: var(--pri-d); }
.qnum { font-weight: 700; color: var(--pri-d); }

/* ---------- hộp thoại */
.modal { position: fixed; inset: 0; background: rgba(15, 25, 45, .45); display: grid; place-items: center; z-index: 50; padding: 16px; }
.modal .box { background: #fff; border-radius: 16px; padding: 18px; width: 100%; max-width: 440px; }
.modal textarea { width: 100%; min-height: 90px; border: 1px solid var(--line); border-radius: 10px; padding: 10px; margin-top: 8px; }
.toast { position: fixed; left: 50%; bottom: 22px; transform: translateX(-50%); background: #1d2433; color: #fff; padding: 10px 16px; border-radius: 12px; z-index: 60; font-size: 14px; max-width: calc(100% - 32px); }

/* ---------- admin */
table.tb { width: 100%; border-collapse: collapse; font-size: 14px; }
table.tb th, table.tb td { border-bottom: 1px solid var(--line); padding: 8px 6px; text-align: left; vertical-align: top; }
table.tb th { background: var(--bg); position: sticky; top: 0; }
.scroll { overflow-x: auto; }
.filters { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 10px; }
.filters select, .filters input { padding: 8px 10px; border: 1px solid var(--line); border-radius: 10px; background: #fff; }
.pill { display: inline-block; border-radius: 99px; padding: 1px 9px; font-size: 12px; font-weight: 600; }
.pill.on { background: var(--ok-l); color: var(--ok); }
.pill.off { background: var(--bad-l); color: var(--bad); }
.atabs { display: flex; gap: 6px; overflow-x: auto; margin-top: 14px; padding-bottom: 4px; }
.atabs button { border: 1px solid var(--line); background: #fff; border-radius: 10px; padding: 8px 12px; white-space: nowrap; font-weight: 600; font-size: 14px; }
.atabs button.on { background: var(--pri); color: #fff; border-color: var(--pri); }
.svgfig { color: #24324f; }
a.btn { text-decoration: none; display: inline-block; color: inherit; }
.passage { background: var(--bg); border: 1px solid var(--line); border-radius: 12px; padding: 12px 14px; white-space: pre-line; line-height: 1.6; margin-bottom: 12px; max-height: 420px; overflow-y: auto; }
.passage.poem { text-align: center; font-style: italic; }
.mi { border-top: 1px dashed var(--line); padding: 10px 0; }
.mi:first-child { border-top: 0; }
.mi-q { font-weight: 600; margin-bottom: 7px; }
.mi-o { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 6px; }
.opt.sm { padding: 7px 9px; }
.opt.sm .lt { width: 22px; height: 22px; font-size: 12px; }
.q-text u, .ot u { text-decoration-thickness: 2px; text-underline-offset: 3px; }