/* ==========================================================
   Học Tiếng Anh — giai đoạn 0
   Nút to, chữ to, tương phản cao: người dùng là trẻ 9–10 tuổi.
   ========================================================== */
:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --line: #e3e7ef;
  --ink: #161d2e;
  --ink-soft: #5a6479;
  --ink-dim: #8b93a5;
  --brand: #2563eb;
  --brand-ink: #ffffff;
  --good: #12864f;
  --good-bg: #e7f7ee;
  --bad: #c2264a;
  --bad-bg: #fdeaee;
  --warn: #9a6207;
  --shadow: 0 2px 10px rgba(22, 29, 46, .06);
  --radius: 14px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0e1220; --panel: #161b2c; --line: #262d42;
    --ink: #eef1f7; --ink-soft: #a4adc2; --ink-dim: #6e778d;
    --brand: #5b8cff; --brand-ink: #0b1020;
    --good: #57d193; --good-bg: #10291f;
    --bad: #ff8098;  --bad-bg: #2b1420;
    --warn: #e0b25a;
    --shadow: 0 2px 14px rgba(0, 0, 0, .3);
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg); color: var(--ink);
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans", sans-serif;
  -webkit-text-size-adjust: 100%;
}

.top {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  padding: .8rem 1.1rem; background: var(--panel); border-bottom: 1px solid var(--line);
  position: sticky; top: 0; z-index: 10;
}
.brand { display: flex; align-items: center; gap: .5rem; font-weight: 700; color: var(--ink); text-decoration: none; }
.brand .dot { width: 10px; height: 10px; border-radius: 50%; background: var(--brand); }
.top nav { display: flex; gap: .35rem; }
.top nav a {
  color: var(--ink-soft); text-decoration: none; font-size: .88rem;
  padding: .35rem .7rem; border-radius: 8px;
}
.top nav a:hover { background: var(--bg); color: var(--ink); }

.wrap { max-width: 760px; margin: 0 auto; padding: 1.4rem 1.1rem 3rem; }
.foot { text-align: center; color: var(--ink-dim); font-size: .78rem; padding: 0 1rem 2rem; }

h1 { font-size: 1.5rem; margin: .2rem 0 1rem; letter-spacing: -.01em; }
h2 { font-size: 1.05rem; margin: 1.8rem 0 .7rem; }
p  { margin: .5rem 0; }
code { background: var(--bg); padding: .1rem .35rem; border-radius: 5px; font-size: .88em; }
pre {
  background: var(--bg); border: 1px solid var(--line); border-radius: 10px;
  padding: .8rem .9rem; overflow-x: auto; font-size: .82rem; line-height: 1.7;
}
kbd {
  border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 5px;
  padding: .05rem .35rem; font-size: .78rem; background: var(--panel);
}
.hint { color: var(--ink-soft); font-size: .86rem; }

/* ---------- ô số liệu ---------- */
.tiles { display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: .7rem; margin: 1rem 0; }
.tile {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: .8rem .9rem; display: flex; flex-direction: column; gap: .1rem;
}
.tile .l { font-size: .7rem; text-transform: uppercase; letter-spacing: .07em; color: var(--ink-dim); }
.tile .v { font-size: 1.6rem; font-weight: 700; font-variant-numeric: tabular-nums; line-height: 1.15; }
.tile .n { font-size: .78rem; color: var(--ink-soft); }

/* ---------- danh sách unit ---------- */
.units { display: grid; gap: .7rem; }
.unit {
  display: grid; gap: .2rem; text-decoration: none; color: var(--ink);
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1rem 1.1rem; transition: transform .12s ease, border-color .12s ease;
}
.unit:hover { transform: translateY(-2px); border-color: var(--brand); }
.unit strong { font-size: 1.12rem; }
.unit .sub { color: var(--ink-soft); font-size: .9rem; }
.unit .meta { color: var(--ink-dim); font-size: .8rem; margin-top: .2rem; }
.unit .go { color: var(--brand); font-weight: 600; font-size: .9rem; margin-top: .4rem; }

.badge {
  display: inline-block; font-size: .7rem; font-weight: 600; letter-spacing: .04em;
  background: var(--brand); color: var(--brand-ink); padding: .12rem .5rem; border-radius: 999px;
  width: fit-content;
}
.badge.soft { background: var(--bg); color: var(--ink-soft); border: 1px solid var(--line); }

/* ---------- thẻ ---------- */
.card {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.1rem 1.2rem; box-shadow: var(--shadow); margin: .9rem 0;
}
.card.empty p:first-child { margin-top: 0; }

/* ---------- tiến độ buổi học ---------- */
.progress { height: 8px; background: var(--line); border-radius: 999px; overflow: hidden; margin-bottom: .7rem; }
.progress span { display: block; height: 100%; background: var(--brand); border-radius: 999px; transition: width .3s ease; }
.step { color: var(--ink-soft); font-size: .84rem; margin: 0 0 .2rem; }

/* ---------- câu hỏi ---------- */
.prompt { font-size: 1.3rem; font-weight: 600; line-height: 1.5; margin: .3rem 0 1rem; }
.options { display: grid; gap: .55rem; }
.opt {
  display: flex; align-items: center; gap: .7rem; width: 100%; text-align: left;
  font: inherit; font-size: 1.06rem; color: var(--ink); cursor: pointer;
  background: var(--panel); border: 2px solid var(--line); border-radius: 12px;
  padding: .85rem 1rem; transition: border-color .12s ease, transform .08s ease;
}
.opt:hover { border-color: var(--brand); }
.opt:active { transform: scale(.99); }
.opt .key {
  flex: none; width: 26px; height: 26px; border-radius: 7px; background: var(--bg);
  display: grid; place-items: center; font-size: .82rem; font-weight: 700; color: var(--ink-soft);
}

.text {
  width: 100%; font: inherit; font-size: 1.2rem; padding: .8rem .9rem;
  border: 2px solid var(--line); border-radius: 12px; background: var(--panel); color: var(--ink);
}
.text:focus { outline: none; border-color: var(--brand); }

/* ---------- sắp xếp từ ---------- */
.slot {
  min-height: 62px; border: 2px dashed var(--line); border-radius: 12px;
  padding: .55rem; display: flex; flex-wrap: wrap; gap: .4rem; align-content: flex-start;
  margin-bottom: .8rem;
}
.cards { display: flex; flex-wrap: wrap; gap: .4rem; }
.card-word {
  font: inherit; font-size: 1.05rem; cursor: pointer; color: var(--ink);
  background: var(--panel); border: 2px solid var(--line); border-radius: 10px;
  padding: .5rem .8rem; transition: border-color .12s ease, opacity .12s ease;
}
.card-word:hover { border-color: var(--brand); }
.card-word.used { opacity: .28; pointer-events: none; }
.slot .card-word { background: var(--bg); border-style: solid; border-color: var(--brand); }

/* ---------- nút ---------- */
.btn {
  display: inline-block; font: inherit; font-size: 1rem; font-weight: 600; cursor: pointer;
  padding: .7rem 1.2rem; border-radius: 11px; border: 2px solid transparent; text-decoration: none;
}
.btn.primary { background: var(--brand); color: var(--brand-ink); }
.btn.primary:disabled { opacity: .4; cursor: not-allowed; }
.btn.ghost { background: transparent; border-color: var(--line); color: var(--ink-soft); }
.btn.danger { background: var(--bad-bg); color: var(--bad); border-color: transparent; }
.row { display: flex; gap: .6rem; flex-wrap: wrap; align-items: center; margin-top: 1rem; }
.quit { text-align: center; margin-top: 1.6rem; }
.quit a { color: var(--ink-dim); font-size: .84rem; }

/* ---------- phản hồi ---------- */
.card.fb { border-width: 2px; }
.card.fb.good { border-color: var(--good); background: var(--good-bg); }
.card.fb.bad  { border-color: var(--bad);  background: var(--bad-bg); }
.fb-head { font-size: 1.3rem; font-weight: 700; margin-bottom: .3rem; }
.fb.good .fb-head { color: var(--good); }
.fb.bad  .fb-head { color: var(--bad); }
.fb-line { font-size: 1.05rem; }
.fb-explain { color: var(--ink-soft); }
.card.fb .btn { margin-top: .8rem; }

/* ---------- kết quả ---------- */
.bars { display: grid; gap: .5rem; }
.bar-row { display: grid; grid-template-columns: 1fr 120px 42px; gap: .7rem; align-items: center; font-size: .88rem; }
.bar { height: 9px; background: var(--line); border-radius: 999px; overflow: hidden; }
.bar .fill { display: block; height: 100%; border-radius: 999px; }
.bar .fill.hi  { background: var(--good); }
.bar .fill.mid { background: var(--warn); }
.bar .fill.lo  { background: var(--bad); }
.bar-val { text-align: right; color: var(--ink-soft); font-variant-numeric: tabular-nums; font-size: .82rem; }

.review { list-style: none; padding: 0; margin: .5rem 0; display: grid; gap: .35rem; }
.review li { display: flex; gap: .6rem; align-items: flex-start; font-size: .92rem;
             background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: .55rem .75rem; }
.review .mark { flex: none; font-weight: 700; }
.review li.ok .mark { color: var(--good); }
.review li.no .mark { color: var(--bad); }
.review em { display: block; color: var(--ink-soft); font-style: normal; font-size: .84rem; margin-top: .15rem; }

/* ---------- màn duyệt ---------- */
.card.item { border-left: 4px solid var(--warn); }
.item-head { display: flex; gap: .4rem; align-items: center; flex-wrap: wrap; margin-bottom: .5rem; }
.item-head .id { margin-left: auto; color: var(--ink-dim); font-size: .8rem; font-variant-numeric: tabular-nums; }
.grammar { color: var(--ink-soft); font-size: .84rem; margin: 0 0 .3rem; }
.opts { list-style: none; padding: 0; margin: .4rem 0; display: grid; gap: .2rem; font-size: .95rem; }
.opts li { padding: .3rem .55rem; border-radius: 7px; }
.opts li.right { background: var(--good-bg); color: var(--good); font-weight: 600; }
.ans { font-size: .95rem; }
.explain { color: var(--ink-soft); font-size: .88rem; border-left: 3px solid var(--line); padding-left: .7rem; }
.issues { list-style: none; padding: 0; margin: .6rem 0; display: grid; gap: .25rem; font-size: .82rem; }
.issues li { padding: .35rem .6rem; border-radius: 7px; background: var(--bg); }
.issues li.error { color: var(--bad); }
.issues li.warn  { color: var(--warn); }
.judge { font-size: .86rem; color: var(--ink-soft); background: var(--bg); border-radius: 8px; padding: .5rem .7rem; }

@media (max-width: 520px) {
  .wrap { padding: 1rem .8rem 2.5rem; }
  .prompt { font-size: 1.15rem; }
  .bar-row { grid-template-columns: 1fr 70px 38px; }
}