:root {
  --bg: #fdf8f0;
  --card: #ffffff;
  --ink: #2d2a26;
  --muted: #7a7268;
  --line: #ece4d6;
  --accent: #ff8a3d;
  --accent-ink: #ffffff;
  --good: #2e9e5b;
  --good-bg: #e6f6ec;
  --bad: #d4553a;
  --bad-bg: #fdecE7;
  --math: #4f8df7;
  --chinese: #e25c5c;
  --english: #33a86b;
  --radius: 18px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1d1b19;
    --card: #2a2724;
    --ink: #f3eee7;
    --muted: #b3aa9f;
    --line: #3b3733;
    --good-bg: #1f3a2a;
    --bad-bg: #432621;
  }
}
* { box-sizing: border-box; }
button, a, .card, .choice { touch-action: manipulation; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  font-size: 18px;
  line-height: 1.5;
}
.top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 16px; padding-top: max(12px, env(safe-area-inset-top)); max-width: 760px; margin: 0 auto;
}
.brand { font-size: 26px; font-weight: 800; color: var(--accent); text-decoration: none; letter-spacing: 2px; }
.who { color: var(--muted); font-size: 15px; }
main { max-width: 760px; margin: 0 auto; padding: 8px 16px 48px; }
h1 { font-size: 28px; margin: 8px 0 20px; }
h2 { font-size: 20px; margin: 24px 0 12px; }
.muted { color: var(--muted); font-size: 15px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 14px; }
.card {
  background: var(--card); border: 2px solid var(--line); border-radius: var(--radius);
  padding: 18px; text-align: center; cursor: pointer; color: inherit; font: inherit;
  transition: transform .12s ease, border-color .12s ease;
}
.card:hover, .card:focus-visible { transform: translateY(-2px); border-color: var(--accent); outline: none; }
.avatar {
  width: 64px; height: 64px; border-radius: 50%; margin: 0 auto 10px;
  display: grid; place-items: center; font-size: 30px; font-weight: 800; color: #fff;
}
.subject { text-align: left; border-left-width: 8px; }
.subject.math { border-left-color: var(--math); }
.subject.chinese { border-left-color: var(--chinese); }
.subject.english { border-left-color: var(--english); }
.subject .name { font-size: 24px; font-weight: 800; }
.tag {
  display: inline-block; padding: 2px 10px; border-radius: 999px; font-size: 14px;
  background: var(--line); color: var(--ink); margin: 6px 0;
}
.btn {
  appearance: none; border: 0; border-radius: 999px; padding: 12px 24px;
  background: var(--accent); color: var(--accent-ink); font: inherit; font-weight: 700; cursor: pointer;
}
.btn.ghost { background: transparent; color: var(--ink); border: 2px solid var(--line); }
.btn:focus-visible { outline: 3px solid var(--ink); outline-offset: 2px; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 16px; }
form.add { display: grid; gap: 12px; max-width: 360px; }
input, select {
  font: inherit; padding: 10px 14px; border-radius: 12px; border: 2px solid var(--line);
  background: var(--card); color: var(--ink);
}
.progress { display: flex; gap: 8px; margin: 8px 0 20px; }
.dot { width: 18px; height: 18px; border-radius: 50%; background: var(--line); }
.dot.ok { background: var(--good); }
.dot.no { background: var(--bad); }
.dot.now { box-shadow: 0 0 0 3px var(--accent); }
.stem { font-size: 34px; font-weight: 700; margin: 12px 0 24px; word-break: break-word; }
.choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 12px; }
.choice {
  font: inherit; font-size: 24px; font-weight: 700; padding: 18px; border-radius: var(--radius);
  border: 3px solid var(--line); background: var(--card); color: var(--ink); cursor: pointer;
}
.choice:hover, .choice:focus-visible { border-color: var(--accent); outline: none; }
.answer-box { font-size: 32px; width: 100%; text-align: center; padding: 14px; }
.pad { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; margin-top: 14px; }
.pad button {
  font: inherit; font-size: 26px; padding: 14px 0; border-radius: 14px; border: 2px solid var(--line);
  background: var(--card); color: var(--ink); cursor: pointer;
}
.pad button.go { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.feedback { margin-top: 22px; padding: 18px; border-radius: var(--radius); font-size: 22px; font-weight: 700; }
.feedback.good { background: var(--good-bg); color: var(--good); }
.feedback.bad { background: var(--bad-bg); color: var(--bad); }
.stars { font-size: 30px; letter-spacing: 4px; }
.big { font-size: 56px; text-align: center; margin: 12px 0; }
.stat { display: grid; grid-template-columns: repeat(auto-fit, minmax(130px, 1fr)); gap: 10px; }
.stat div { background: var(--card); border: 2px solid var(--line); border-radius: 14px; padding: 12px; }
.stat b { display: block; font-size: 26px; }
ul.plain { padding-left: 20px; margin: 6px 0; }
.error { color: var(--bad); font-weight: 700; }
@media (max-width: 480px) {
  .stem { font-size: 28px; }
  .choice { font-size: 20px; padding: 14px; }
}
.icp { text-align: center; padding: 16px 16px max(16px, env(safe-area-inset-bottom)); font-size: 13px; }
.icp a { color: var(--muted); text-decoration: none; }