:root {
  color-scheme: light;
  --bg: #f6f7f9;
  --panel: #ffffff;
  --text: #1d2430;
  --muted: #687385;
  --line: #d9dee7;
  --brand: #b91c1c;
  --brand-dark: #7f1d1d;
  --focus: #2563eb;
  --ok: #047857;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Microsoft YaHei", "PingFang SC", Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
}

header {
  background: var(--panel);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 5;
}

.topbar {
  max-width: 1120px;
  margin: 0 auto;
  padding: 18px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

h1,
h2,
h3 {
  margin: 0;
  line-height: 1.25;
}

h1 {
  font-size: 22px;
}

h2 {
  font-size: 20px;
  margin-bottom: 16px;
}

h3 {
  font-size: 18px;
  margin-bottom: 14px;
}

.subtle,
.meta {
  color: var(--muted);
  font-size: 14px;
}

main {
  max-width: 1120px;
  margin: 0 auto;
  padding: 24px 20px 64px;
}

.panel,
.question,
.section {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
}

.panel {
  padding: 20px;
  margin-bottom: 18px;
}

.student-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-weight: 700;
}

input,
textarea,
select {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 6px;
  font: inherit;
  padding: 10px 12px;
  background: #fff;
  color: var(--text);
}

textarea {
  min-height: 96px;
  resize: vertical;
}

input:focus,
textarea:focus,
select:focus {
  outline: 3px solid rgba(37, 99, 235, 0.18);
  border-color: var(--focus);
}

.tabs {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.tab,
button,
.link-button {
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 9px 14px;
  background: #fff;
  color: var(--text);
  cursor: pointer;
  font: inherit;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.tab.active,
button.primary {
  background: var(--brand);
  border-color: var(--brand);
  color: #fff;
}

button.primary:hover,
.tab.active:hover {
  background: var(--brand-dark);
}

.section {
  padding: 18px;
  margin-bottom: 18px;
}

.passage {
  white-space: pre-line;
  background: #f8fafc;
  border-left: 4px solid #94a3b8;
  padding: 14px 16px;
  margin: 0 0 16px;
}

.question {
  padding: 16px;
  margin: 12px 0;
}

.question-title {
  display: grid;
  grid-template-columns: 42px 1fr;
  gap: 10px;
  align-items: start;
  margin-bottom: 12px;
}

.number {
  display: inline-grid;
  place-items: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: #fee2e2;
  color: var(--brand-dark);
  font-weight: 800;
}

.prompt {
  white-space: pre-line;
  font-weight: 700;
}

.options {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.option {
  display: grid;
  grid-template-columns: 22px 1fr;
  align-items: center;
  gap: 8px;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  font-weight: 500;
}

.option input {
  width: auto;
}

.formula {
  max-height: 34px;
  vertical-align: middle;
  margin: 0 4px;
}

.math-inline {
  display: inline-block;
  margin: 0 4px;
  font-family: "Cambria Math", "Times New Roman", serif;
  font-size: 1.08em;
  font-weight: 700;
}

.math-block {
  display: block;
  margin-top: 8px;
  font-family: "Cambria Math", "Times New Roman", serif;
  font-size: 1.06em;
  font-weight: 700;
}

.formula.small {
  max-height: 22px;
}

.formula.wide {
  max-height: 40px;
}

.formula.block,
.diagram {
  display: block;
  max-width: min(100%, 440px);
  max-height: none;
  margin: 12px 0 4px;
}

.formula.large {
  max-width: min(100%, 520px);
}

.diagram {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 8px;
  background: #fff;
}

.suffix-row {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: 10px;
}

.actions {
  position: sticky;
  bottom: 0;
  background: rgba(246, 247, 249, 0.92);
  backdrop-filter: blur(8px);
  border-top: 1px solid var(--line);
  padding: 14px 0 0;
  display: flex;
  justify-content: flex-end;
  gap: 10px;
}

.status {
  color: var(--ok);
  font-weight: 700;
  margin-right: auto;
}

.status.error {
  color: var(--brand);
}

.admin-tools {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 18px;
}

.score-table {
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.score-row {
  display: grid;
  grid-template-columns: 56px 1.2fr 1fr 1fr repeat(4, 72px);
  gap: 10px;
  align-items: center;
  padding: 10px 12px;
  border-bottom: 1px solid var(--line);
}

.score-row:last-child {
  border-bottom: 0;
}

.score-head {
  background: #f8fafc;
  color: var(--muted);
  font-weight: 700;
}

.grade-form {
  display: grid;
  grid-template-columns: repeat(3, minmax(92px, 120px)) minmax(160px, 1fr) auto auto;
  gap: 10px;
  align-items: end;
  padding: 14px;
  margin: 12px 0 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f8fafc;
}

.grade-form label {
  font-size: 14px;
}

.grade-status {
  min-width: 60px;
  color: var(--ok);
  font-weight: 700;
}

.grade-status.error {
  color: var(--brand);
}

.response-list {
  display: grid;
  gap: 14px;
}

.response {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
}

.answer-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px 18px;
}

.answer {
  border-bottom: 1px solid #edf0f5;
  padding: 6px 0;
  word-break: break-word;
}

@media (max-width: 760px) {
  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .student-grid,
  .options,
  .answer-grid,
  .grade-form,
  .score-row {
    grid-template-columns: 1fr;
  }
}