:root {
  --ink: #17211b;
  --muted: #667068;
  --paper: #f4f2ea;
  --card: #fffdf8;
  --acid: #d8f36a;
  --orange: #f28c5b;
  --line: #d8ddd2;
  --danger: #9b3d32;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: 'Noto Serif CJK SC', 'Source Han Serif SC', 'Songti SC', STSong, SimSun, Georgia, serif; }
.practice-header { min-height: 76px; border-bottom: 1px solid var(--line); display: flex; align-items: center; justify-content: space-between; padding: 0 6vw; background: rgba(248,247,240,.97); }
.practice-brand { display: grid; justify-items: center; gap: .24rem; color: var(--ink); text-decoration: none; text-align: center; line-height: 1.05; }
.practice-brand .brand-main { font: 800 15px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; letter-spacing: .07em; white-space: nowrap; }
.practice-brand small { color: var(--muted); font: 700 10px Arial, sans-serif; letter-spacing: .055em; white-space: nowrap; }
.practice-header-actions { display: flex; align-items: center; gap: .9rem; }
.header-button { background: transparent; padding: .55rem .75rem; }
.controlled-label, .kicker { font: 700 11px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; letter-spacing: .08em; color: #bd5d35; }
.practice-shell { width: min(900px, 90vw); margin: 0 auto; padding: 5rem 0 7rem; }
.practice-intro { max-width: 720px; margin-bottom: 3rem; }
.practice-intro h1 { font-size: clamp(3.4rem, 8vw, 6.4rem); line-height: .92; letter-spacing: -.05em; margin: .9rem 0 1.2rem; }
.practice-intro p, .muted { color: var(--muted); line-height: 1.6; }
.panel { background: var(--card); border: 1px solid var(--line); padding: clamp(1.4rem, 4vw, 2.5rem); margin-top: 1rem; }
.panel h2 { font-size: clamp(1.8rem, 4vw, 2.8rem); line-height: 1; margin: .4rem 0 1.2rem; }
#access-form { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 1rem; margin-top: 2rem; }
#access-form label:first-child { grid-column: 1 / -1; }
label { font: 700 12px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; letter-spacing: .02em; }
label > span:first-child { font-weight: 700; color: var(--ink); }
label > span + span { font-weight: 400; color: var(--muted); }
input, textarea { width: 100%; margin-top: .45rem; border: 1px solid #bfc7bd; background: white; color: var(--ink); padding: .85rem .9rem; font: 16px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; border-radius: 0; }
input:focus, textarea:focus { outline: 3px solid var(--orange); outline-offset: 1px; }
button { border: 1px solid var(--ink); background: var(--acid); color: var(--ink); padding: .85rem 1.2rem; font: 800 12px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; letter-spacing: .02em; cursor: pointer; width: fit-content; }
button:hover { box-shadow: 4px 4px 0 var(--ink); transform: translate(-1px,-1px); }
button:disabled { opacity: .5; cursor: wait; box-shadow: none; transform: none; }
#access-form button { grid-column: 1 / -1; margin-top: .5rem; }
.error { color: var(--danger); font: 700 13px Arial, sans-serif; margin: 1rem 0 0; }
.assignment-choices { display: grid; gap: .7rem; margin-top: 1.4rem; }
.assignment-choice { width: 100%; text-align: left; background: #fbfaf5; border: 1px solid var(--line); padding: 1rem 1.1rem; display: grid; gap: .35rem; }
.assignment-choice strong { font-size: .95rem; }
.assignment-choice span { color: var(--muted); font-weight: 400; }
.assignment-heading { display: flex; justify-content: space-between; gap: 1rem; align-items: flex-start; margin-bottom: 2rem; }
.assignment-heading h2 { max-width: 650px; }
.attempt-label { background: var(--ink); color: var(--paper); padding: .55rem .7rem; font: 700 10px Arial, sans-serif; text-transform: uppercase; letter-spacing: .08em; white-space: nowrap; }
.timer-label { font-variant-numeric: tabular-nums; }
.assignment-meta { display: grid; justify-items: end; gap: .55rem; }
.progress-wrap { width: min(210px, 42vw); display: grid; gap: .38rem; }
.progress-label { color: var(--muted); font: 700 11px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; text-align: right; }
.progress-track { height: 7px; border: 1px solid var(--ink); background: var(--card); overflow: hidden; }
.progress-track span { display: block; width: 0; height: 100%; background: var(--acid); transition: width .18s ease; }
.save-status { color: var(--muted); font: 600 11px 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; }
.save-status.is-saving { color: #bd5d35; }
.save-status.is-error { color: var(--danger); }
.secondary-button { background: transparent; }
.history-heading { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; }
.history-heading h2 { margin-bottom: 0; }
.attempt-history { display: grid; gap: .65rem; margin-top: 1.5rem; }
.history-item { display: grid; grid-template-columns: 1fr auto; gap: 1rem; align-items: center; padding: .9rem 1rem; border: 1px solid var(--line); background: #fbfaf5; }
.history-item strong { display: block; margin-bottom: .25rem; }
.history-item span { color: var(--muted); font-size: .9rem; }
.history-item button { padding: .55rem .8rem; }
.history-item time { display: block; margin-top: .25rem; color: var(--muted); font: 600 11px Arial, sans-serif; }
.question { border: 0; border-top: 1px solid var(--line); padding: 2rem 0; margin: 0; }
.question.is-answered { box-shadow: inset 4px 0 0 var(--acid); padding-left: 1rem; padding-right: .35rem; }
.question.needs-answer { box-shadow: inset 4px 0 0 var(--orange); padding-left: 1rem; padding-right: .35rem; }
.question legend { width: 100%; font-size: 1.22rem; line-height: 1.45; font-weight: 700; padding: 0; }
.question legend > span { display: inline-flex; width: 28px; height: 28px; align-items: center; justify-content: center; background: var(--orange); margin-right: .7rem; font: 800 11px Arial, sans-serif; vertical-align: .15em; }
.question-language-row { margin-top: .8rem; display: flex; flex-wrap: wrap; align-items: center; gap: .7rem; }
.question-language-toggle { background: transparent; padding: .45rem .65rem; border-color: var(--line); }
.translation-note { color: var(--muted); font: 600 11px 'Noto Sans CJK SC', 'Microsoft YaHei', Arial, sans-serif; }
.alternate-question { margin-top: .8rem; padding: .9rem 1rem; border-left: 3px solid var(--orange); background: #fbfaf5; }
.alternate-question p { margin: 0; line-height: 1.6; }
.alternate-options { margin: .7rem 0 0; padding-left: 1.5rem; color: var(--muted); }
.alternate-options li { margin: .35rem 0; line-height: 1.5; }
.options { display: grid; gap: .55rem; margin-top: 1.2rem; }
.option { display: grid; grid-template-columns: 22px 1fr; gap: .7rem; align-items: start; padding: .8rem .9rem; border: 1px solid var(--line); background: #fbfaf5; font-family: 'Noto Sans CJK SC', 'Source Han Sans SC', 'Microsoft YaHei', Arial, sans-serif; font-size: 14px; font-weight: 400; line-height: 1.55; }
.option:has(input:checked) { border-color: var(--ink); box-shadow: inset 4px 0 0 var(--acid); }
.option input { width: auto; margin: .15rem 0 0; }
.numeric-answer, .open-answer { display: block; margin-top: 1.2rem; max-width: 480px; }
.numeric-answer span { display: block; margin-top: .4rem; color: var(--muted); font-weight: 400; }
.submit-row { display: flex; justify-content: space-between; align-items: center; gap: 1.2rem; padding-top: 1.2rem; border-top: 1px solid var(--line); }
.submit-row p { margin: 0; }
.submit-row button { flex: 0 0 auto; }
.result-actions { display: flex; flex-wrap: wrap; align-items: center; gap: .7rem 1rem; margin-top: 1.8rem; }
.result-actions .back-link { margin-top: 0; }
.result-panel h2 { font-size: clamp(3rem, 8vw, 5.5rem); margin: .7rem 0 1.5rem; }
.feedback-list { display: grid; gap: .7rem; }
.feedback-item { border: 1px solid var(--line); padding: 1rem; background: #fbfaf5; }
.feedback-item > div { display: flex; justify-content: space-between; gap: 1rem; font: 700 11px Arial, sans-serif; text-transform: uppercase; letter-spacing: .06em; }
.feedback-item.is-correct { box-shadow: inset 4px 0 0 var(--acid); }
.feedback-item.needs-review { box-shadow: inset 4px 0 0 var(--orange); }
.feedback-item p { color: var(--muted); line-height: 1.5; margin: .7rem 0; }
.feedback-item small { font-family: Arial, sans-serif; color: var(--ink); }
.back-link { display: inline-block; margin-top: 1.8rem; color: var(--ink); font: 700 12px Arial, sans-serif; }
[hidden] { display: none !important; }

@media (max-width: 640px) {
  .practice-header { padding: 14px 5vw; gap: 1rem; }
  .controlled-label { text-align: right; }
  .practice-header-actions { gap: .55rem; }
  .practice-brand small { display: none; }
  .header-button { padding: .48rem .62rem; }
  .practice-shell { width: 90vw; padding-top: 3.5rem; }
  #access-form { grid-template-columns: 1fr; }
  #access-form label:first-child, #access-form button { grid-column: auto; }
  .assignment-heading { display: block; }
  .assignment-meta { justify-items: start; margin-bottom: 1rem; }
  .attempt-label { display: inline-block; }
  .progress-wrap { width: min(240px, 100%); }
  .progress-label { text-align: left; }
  .submit-row { align-items: stretch; flex-direction: column; }
  .submit-row button { width: 100%; }
  .history-item { grid-template-columns: 1fr; }
  .history-item button { width: 100%; }
  .question legend { font-size: 1.08rem; }
}