:root {
  --ink: #17211b;
  --muted: #66736b;
  --paper: #f7f8f4;
  --surface: #ffffff;
  --line: #d9dfd7;
  --circuit: #0f766e;
  --network: #2456a6;
  --sensor: #b45f06;
  --danger: #b42318;
  --success: #15803d;
  --focus: #f59e0b;
  --shadow: 0 1rem 2rem rgba(23, 33, 27, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    linear-gradient(90deg, rgba(15, 118, 110, 0.08) 1px, transparent 1px),
    linear-gradient(180deg, rgba(36, 86, 166, 0.07) 1px, transparent 1px),
    var(--paper);
  background-size: 2.25rem 2.25rem;
  font-family: "Microsoft YaHei", "PingFang SC", system-ui, sans-serif;
  line-height: 1.6;
}

button,
input,
textarea,
select {
  font: inherit;
}

button {
  cursor: pointer;
}

button:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 0.18rem solid var(--focus);
  outline-offset: 0.16rem;
}

.app-shell {
  width: min(100%, 86rem);
  margin: 0 auto;
  padding: 1rem;
}

.topbar {
  display: grid;
  gap: 1rem;
  padding: 1.2rem 0 1rem;
}

.eyebrow {
  margin: 0 0 0.25rem;
  color: var(--circuit);
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0;
  font-family: "Microsoft JhengHei", "Microsoft YaHei", system-ui, sans-serif;
  font-size: 1.85rem;
  line-height: 1.18;
}

.summary-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.55rem;
}

.summary-strip span {
  min-width: 0;
  padding: 0.65rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: rgba(255, 255, 255, 0.74);
  color: var(--muted);
  text-align: center;
}

.summary-strip strong {
  display: block;
  color: var(--ink);
  font-size: 1.15rem;
  line-height: 1.1;
}

.study-layout {
  display: grid;
  gap: 1rem;
  min-width: 0;
}

.control-panel,
.stage-card {
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: rgba(255, 255, 255, 0.92);
  box-shadow: var(--shadow);
}

.control-panel {
  padding: 1rem;
  min-width: 0;
  overflow: hidden;
}

.panel-section + .panel-section {
  margin-top: 1.15rem;
  padding-top: 1.15rem;
  border-top: 1px solid var(--line);
}

.panel-section h2 {
  margin-bottom: 0.55rem;
  font-size: 0.94rem;
}

.action-grid {
  display: grid;
  gap: 0.5rem;
}

.secondary-button,
.primary-button,
.map-button {
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background: var(--surface);
  color: var(--ink);
}

.select-field {
  display: grid;
  gap: 0.35rem;
}

.select-field span {
  color: var(--muted);
  font-size: 0.82rem;
}

.select-field select {
  width: 100%;
  min-height: 2.75rem;
  padding: 0.62rem 2.25rem 0.62rem 0.72rem;
  border: 1px solid var(--line);
  border-radius: 0.45rem;
  background:
    linear-gradient(45deg, transparent 50%, var(--circuit) 50%) calc(100% - 1.05rem) 50% / 0.45rem 0.45rem no-repeat,
    linear-gradient(135deg, var(--circuit) 50%, transparent 50%) calc(100% - 0.78rem) 50% / 0.45rem 0.45rem no-repeat,
    var(--surface);
  color: var(--ink);
  appearance: none;
}

.secondary-button,
.primary-button {
  min-height: 2.7rem;
  padding: 0.65rem 0.9rem;
  font-weight: 700;
}

.secondary-button:hover,
.select-field select:hover,
.map-button:hover {
  border-color: var(--circuit);
}

.secondary-button.danger {
  color: var(--danger);
}

.primary-button {
  width: 100%;
  border-color: var(--circuit);
  background: var(--circuit);
  color: #fff;
}

.primary-button:disabled {
  cursor: not-allowed;
  opacity: 0.58;
}

.question-map {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(2.35rem, 1fr));
  gap: 0.42rem;
  width: 100%;
  min-width: 0;
  max-width: 100%;
  max-height: calc(2.35rem * 3 + 0.42rem * 2);
  overflow-x: hidden;
  overflow-y: auto;
  padding-right: 0.2rem;
  scroll-snap-type: y proximity;
}

.map-button {
  aspect-ratio: 1;
  min-width: 0;
  padding: 0;
  font-size: 0.82rem;
  font-weight: 700;
  scroll-snap-align: start;
}

.map-button.current {
  border-color: var(--network);
  background: rgba(36, 86, 166, 0.12);
  color: var(--network);
}

.map-button.done {
  border-color: rgba(21, 128, 61, 0.5);
}

.map-button.correct {
  border-color: var(--success);
  background: var(--success);
  color: #fff;
}

.map-button.wrong {
  border-color: var(--danger);
  background: var(--danger);
  color: #fff;
}

.map-button.current.correct,
.map-button.current.wrong {
  outline: 0.16rem solid var(--network);
  outline-offset: 0.12rem;
}

.question-stage {
  min-width: 0;
}

.stage-card {
  min-height: 34rem;
  padding: 1rem;
}

.question-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-bottom: 1rem;
}

.question-meta span {
  padding: 0.26rem 0.55rem;
  border: 1px solid var(--line);
  border-radius: 999rem;
  background: #f8faf8;
  color: var(--muted);
  font-size: 0.82rem;
}

.question-title {
  margin-bottom: 1rem;
  font-size: 1.25rem;
  line-height: 1.55;
}

.image-list {
  display: grid;
  gap: 0.8rem;
  margin: 0.7rem 0 1rem;
}

.image-list:empty {
  display: none;
}

.image-list figure {
  margin: 0;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: #fdfdfb;
}

.image-list img {
  display: block;
  width: 100%;
  height: auto;
  max-height: 34rem;
  object-fit: contain;
}

.image-list figcaption {
  padding: 0.45rem 0.65rem;
  color: var(--muted);
  font-size: 0.82rem;
}

.answer-area {
  display: grid;
  gap: 0.85rem;
}

.option-list {
  display: grid;
  gap: 0.65rem;
}

.option-item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.7rem;
  align-items: start;
  padding: 0.78rem;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
}

.option-item input {
  margin-top: 0.3rem;
}

.option-key {
  display: inline-grid;
  place-items: center;
  width: 1.85rem;
  height: 1.85rem;
  border-radius: 0.4rem;
  background: rgba(15, 118, 110, 0.09);
  color: var(--circuit);
  font-weight: 800;
}

.blank-input,
.subjective-input {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 0.5rem;
  background: var(--surface);
  color: var(--ink);
}

.blank-input {
  min-height: 3rem;
  padding: 0.7rem 0.8rem;
}

.subjective-input {
  min-height: 11rem;
  padding: 0.85rem;
  resize: vertical;
}

.form-message {
  min-height: 1.5rem;
  margin-bottom: 0;
  color: var(--danger);
  font-size: 0.9rem;
}

.feedback-panel {
  margin-top: 1rem;
  padding: 1rem;
  border: 1px solid rgba(15, 118, 110, 0.35);
  border-radius: 0.5rem;
  background: rgba(15, 118, 110, 0.08);
}

.feedback-panel.wrong {
  border-color: rgba(180, 35, 24, 0.35);
  background: rgba(180, 35, 24, 0.07);
}

.feedback-heading {
  display: grid;
  gap: 0.35rem;
  margin-bottom: 0.65rem;
}

.feedback-badge {
  width: fit-content;
  padding: 0.22rem 0.55rem;
  border-radius: 999rem;
  background: var(--surface);
  color: var(--circuit);
  font-size: 0.82rem;
  font-weight: 800;
}

.feedback-panel.wrong .feedback-badge {
  color: var(--danger);
}

#feedbackText,
#correctAnswerText {
  white-space: pre-line;
}

.stage-actions {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.65rem;
  margin-top: 1rem;
}

.empty-state {
  padding: 1rem;
  border: 1px dashed var(--line);
  border-radius: 0.5rem;
  color: var(--muted);
  background: rgba(255, 255, 255, 0.7);
}

@media (min-width: 48rem) {
  .app-shell {
    padding: 1.5rem;
  }

  .topbar {
    grid-template-columns: 1fr minmax(19rem, 27rem);
    align-items: end;
  }

  h1 {
    font-size: 2.35rem;
  }

  .study-layout {
    grid-template-columns: minmax(16rem, 19rem) minmax(0, 1fr);
    align-items: start;
  }

  .control-panel {
    position: sticky;
    top: 1rem;
    max-height: calc(100vh - 2rem);
    overflow: auto;
  }

  .question-map {
    grid-template-columns: repeat(auto-fill, minmax(2.35rem, 1fr));
    max-height: 18rem;
    overflow: auto;
    padding-right: 0.2rem;
    scroll-snap-type: none;
  }

  .stage-card {
    padding: 1.35rem;
  }
}

@media (min-width: 64rem) {
  .app-shell {
    padding: 2rem;
  }

  .stage-card {
    padding: 1.75rem;
  }

  .question-title {
    font-size: 1.42rem;
  }

  .option-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (prefers-reduced-motion: no-preference) {
  .select-field select,
  .secondary-button,
  .primary-button,
  .map-button,
  .option-item {
    transition:
      border-color 160ms ease,
      background-color 160ms ease,
      transform 160ms ease;
  }

  .secondary-button:hover,
  .primary-button:hover,
  .map-button:hover {
    transform: translateY(-0.05rem);
  }
}