:root {
  color-scheme: light;
  --bg: #f4efe6;
  --paper: #fffdf8;
  --ink: #1f2937;
  --muted: #6b7280;
  --accent: #d97706;
  --accent-deep: #9a3412;
  --line: #d6c7ae;
  --grid-line: #a8a29e;
  --shadow: 0 20px 60px rgba(78, 52, 20, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Noto Sans TC", "Microsoft JhengHei", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(217, 119, 6, 0.12), transparent 24%),
    linear-gradient(180deg, #fbf7ef 0%, var(--bg) 100%);
}

.app-shell {
  width: min(1200px, calc(100vw - 32px));
  margin: 0 auto;
  padding: 32px 0 48px;
}

.hero {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  align-items: end;
  margin-bottom: 24px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  align-items: center;
}

.eyebrow {
  margin: 0 0 8px;
  font-size: 0.9rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-deep);
}

.version-pill {
  display: inline-block;
  margin: 0 0 10px;
  padding: 6px 12px;
  border-radius: 999px;
  background: rgba(217, 119, 6, 0.12);
  color: var(--accent-deep);
  font-size: 0.92rem;
  font-weight: 700;
}

h1 {
  margin: 0;
  font-size: clamp(2rem, 4vw, 3.5rem);
  line-height: 1.1;
}

.subtitle {
  margin: 12px 0 0;
  color: var(--muted);
}

.primary-button {
  border: 0;
  border-radius: 999px;
  background: linear-gradient(135deg, var(--accent), var(--accent-deep));
  color: white;
  font: inherit;
  padding: 14px 22px;
  cursor: pointer;
  box-shadow: var(--shadow);
}

.controls {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 16px;
  padding: 20px;
  border: 1px solid rgba(154, 52, 18, 0.12);
  border-radius: 24px;
  background: rgba(255, 253, 248, 0.85);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
}

.field {
  display: grid;
  gap: 8px;
}

.field-wide {
  grid-column: 1 / -1;
}

.field-hidden {
  display: none;
}

.field span {
  font-weight: 700;
  font-size: 0.95rem;
}

.field input,
.field select {
  width: 100%;
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: white;
  font: inherit;
}

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

.stepper-button {
  width: 100%;
  min-height: 48px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: white;
  color: var(--accent-deep);
  font: inherit;
  font-size: 1.35rem;
  font-weight: 800;
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background 120ms ease;
}

.stepper-button:hover:not(:disabled) {
  transform: translateY(-1px);
  border-color: rgba(217, 119, 6, 0.45);
  background: rgba(255, 248, 235, 0.96);
}

.stepper-button:disabled {
  cursor: not-allowed;
  opacity: 0.45;
}

.field-toggle {
  align-self: end;
}

.helper-card {
  padding: 16px 18px;
  border-radius: 18px;
  border: 1px dashed rgba(154, 52, 18, 0.24);
  background: rgba(255, 255, 255, 0.72);
}

.helper-text {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.toggle-button {
  width: 100%;
  padding: 12px 14px;
  border-radius: 14px;
  border: 1px solid var(--line);
  background: white;
  color: var(--ink);
  font: inherit;
  cursor: pointer;
}

#answerToggle[aria-pressed="true"] {
  border-color: #287251;
  background: #e8f5ec;
  color: #205b41;
  font-weight: 700;
}

#answerToggle[aria-pressed="false"] {
  border-color: #a6b5bf;
  background: #edf1f4;
  color: #40505c;
  font-weight: 700;
}

.secondary-button {
  border: 1px solid rgba(17, 24, 39, 0.96);
  background: linear-gradient(135deg, #111827, #000000);
  color: #facc15;
  font-weight: 800;
  font-size: 1.08rem;
  box-shadow: 0 12px 30px rgba(17, 24, 39, 0.28);
}

.hero-reset-button {
  width: auto;
  min-width: 148px;
  transform: translateY(-1px);
}

.hero-reset-button:hover {
  transform: translateY(-3px);
}

.hero-reset-button:active {
  transform: translateY(-1px);
}

.pages {
  margin-top: 28px;
  display: grid;
  gap: 28px;
  justify-content: center;
}

.page {
  width: 210mm;
  height: 297mm;
  display: flex;
  flex-direction: column;
  background: var(--paper);
  border-radius: 28px;
  padding: 12mm;
  box-shadow: var(--shadow);
}

.page-header {
  display: flex;
  justify-content: space-between;
  align-items: start;
  gap: 12px;
  margin-bottom: 4mm;
}

.page-following .grid {
  margin-top: 0;
}

.page-following .page-header {
  display: none !important;
}

.page-title,
.page-meta {
  margin: 0;
}

.page-heading {
  display: grid;
  gap: 1.5mm;
  flex: 1;
  min-width: 0;
}

.page-title {
  font-size: 2rem;
}

.page-info {
  display: flex;
  flex-wrap: nowrap;
  gap: 8px 16px;
  color: var(--muted);
  font-size: 0.88rem;
  line-height: 1.15;
  min-width: 0;
}

.page-info-item {
  white-space: nowrap;
  font-size: inherit;
}

.page-info-item span {
  font-size: inherit;
}

.page-signature {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 120px;
  color: var(--muted);
  font-weight: 700;
  text-align: center;
}

.signature-label {
  display: grid;
  gap: 2px;
  line-height: 1.1;
}

.pages.hide-signature .page-signature {
  visibility: hidden;
}

.signature-box {
  display: inline-block;
  width: 120px;
  height: 48px;
  border: 1.5px solid var(--grid-line);
  border-radius: 6px;
}

.page-meta {
  color: var(--muted);
  font-weight: 700;
  width: 100%;
  text-align: center;
  margin-top: 6mm;
}

.grid {
  display: grid;
  grid-template-columns: repeat(1, minmax(0, 1fr));
  grid-template-rows: repeat(4, minmax(0, 1fr));
  gap: 8mm;
  flex: 1;
  min-height: 0;
}

.cell {
  position: relative;
  min-height: 0;
  border: 2px solid var(--grid-line);
  border-radius: 22px;
  background:
    linear-gradient(180deg, rgba(217, 119, 6, 0.06), transparent 35%),
    white;
  overflow: hidden;
}

.cell-layout {
  position: absolute;
  inset: 14px 16px 14px 16px;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 0;
}

.question-pane,
.work-pane {
  min-width: 0;
  min-height: 0;
}

.question-pane {
  position: relative;
  padding: 0 12px 0 0;
}

.question-pane.has-image {
  padding: 0;
}

.question-pane.is-paste-target {
  outline: 3px solid rgba(217, 119, 6, 0.3);
  outline-offset: 6px;
  border-radius: 14px;
}

.cell-paste-input {
  position: absolute;
  inset: 0 auto auto 0;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
  resize: none;
  border: 0;
  padding: 0;
  margin: 0;
  background: transparent;
  color: transparent;
}

.work-pane {
  position: relative;
  display: grid;
  grid-template-rows: auto 1fr;
  border-left: 2px solid rgba(168, 162, 158, 0.7);
  background: transparent;
  padding-left: 12px;
}

.work-pane-number {
  position: absolute;
  top: -8px;
  left: 5px;
  z-index: 2;
  display: grid;
  place-items: center;
  min-width: 18px;
  min-height: 18px;
  padding: 2px 3px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid rgba(154, 52, 18, 0.18);
  color: var(--accent-deep);
  font-size: 0.5rem;
  font-weight: 800;
  line-height: 1;
  text-align: center;
}

.work-pane-title {
  padding: 4px 10px 8px 24px;
  color: var(--accent-deep);
  font-size: 0.69rem;
  font-weight: 800;
  text-align: center;
  letter-spacing: 0.04em;
}

.work-pane-body {
  position: relative;
  display: grid;
  grid-template-rows: auto minmax(0, 1fr);
  min-height: 0;
  background: transparent;
}

.work-answer-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 5px;
  padding: 4px 0 6px;
}

.work-answer-content {
  width: 100%;
  min-height: 0;
  overflow: hidden;
}

.work-answer-text {
  padding: 4px;
  color: #b91c1c;
}

.work-answer-image {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.pages.hide-answers .work-answer-content {
  visibility: hidden;
}

.pages.hide-answers .work-answer-toolbar {
  display: none;
}

.cell-toolbar {
  position: absolute;
  top: 10px;
  left: 54px;
  z-index: 2;
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
  max-width: calc(100% - 76px);
}

.cell-image-paste-button,
.cell-text-paste-button,
.answer-image-paste-button,
.answer-text-paste-button {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  border: 1px solid rgba(217, 119, 6, 0.3);
  background: rgba(255, 248, 235, 0.96);
  color: var(--accent-deep);
  border-radius: 999px;
  padding: 7px 12px;
  font: inherit;
  font-size: 0.82rem;
  font-weight: 700;
  cursor: pointer;
}

.cell-image-paste-button.is-active,
.cell-text-paste-button.is-active {
  background: rgba(217, 119, 6, 0.18);
  border-color: rgba(217, 119, 6, 0.55);
}

.cell-font-stepper {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.cell-font-decrease-button,
.cell-font-increase-button {
  width: 34px;
  height: 34px;
  border-radius: 999px;
  border: 1px solid rgba(217, 119, 6, 0.3);
  background: rgba(255, 248, 235, 0.96);
  color: var(--accent-deep);
  font: inherit;
  font-size: 1.1rem;
  font-weight: 800;
  line-height: 1;
  cursor: pointer;
}

.cell-font-decrease-button:hover,
.cell-font-increase-button:hover {
  border-color: rgba(217, 119, 6, 0.55);
  background: rgba(217, 119, 6, 0.14);
}

.button-icon {
  position: relative;
  width: 14px;
  height: 14px;
  flex: 0 0 14px;
}

.button-icon-image {
  border: 1.5px solid currentColor;
  border-radius: 3px;
}

.button-icon-image::before {
  content: "";
  position: absolute;
  left: 2px;
  bottom: 2px;
  width: 8px;
  height: 5px;
  background: currentColor;
  clip-path: polygon(0 100%, 38% 35%, 56% 62%, 100% 0, 100% 100%);
  opacity: 0.78;
}

.button-icon-image::after {
  content: "";
  position: absolute;
  top: 2px;
  right: 2px;
  width: 2px;
  height: 2px;
  border-radius: 999px;
  background: currentColor;
}

.button-icon-text::before,
.button-icon-text::after {
  content: "";
  position: absolute;
  left: 1px;
  right: 1px;
  height: 1.5px;
  border-radius: 999px;
  background: currentColor;
}

.button-icon-text::before {
  top: 4px;
  box-shadow:
    0 -4px 0 currentColor,
    0 4px 0 currentColor;
}

.button-icon-text::after {
  top: 10px;
  right: 4px;
}

.cell-clear-button,
.answer-clear-button {
  border: 1px solid rgba(154, 52, 18, 0.22);
  background: rgba(255, 255, 255, 0.92);
  color: var(--accent-deep);
  border-radius: 999px;
  padding: 7px 10px;
  font: inherit;
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
}

.cell-content {
  position: relative;
  width: 100%;
  height: 100%;
  margin-top: 44px;
  overflow: hidden;
  white-space: pre-wrap;
  word-break: break-word;
  font-size: clamp(0.9rem, 1vw, 1.08rem);
  line-height: 1.45;
  color: var(--ink);
}

.question-pane.has-question .cell-content {
  display: flex;
  align-items: flex-start;
  padding-right: 8px;
}

.question-pane.has-image .cell-content {
  margin-top: 0;
}

.cell-content.is-empty {
  height: 100%;
}

.problem-text {
  width: 100%;
  height: 100%;
  overflow: hidden;
  padding: 6px 6px 4px 0;
  text-align: left;
  vertical-align: top;
  font-size: 0.92rem;
  line-height: 1.28;
  overflow-wrap: anywhere;
}

.problem-text.is-compact {
  line-height: 1.34;
}

.problem-text p,
.problem-text ul,
.problem-text ol,
.problem-text blockquote {
  margin: 0 0 0.45rem;
}

.problem-text p:last-child,
.problem-text ul:last-child,
.problem-text ol:last-child,
.problem-text blockquote:last-child {
  margin-bottom: 0;
}

.problem-text ul,
.problem-text ol {
  padding-left: 1.25rem;
}

.problem-text strong {
  font-weight: 800;
}

.problem-text .katex-display {
  margin: 0.45rem 0;
  overflow-x: auto;
  overflow-y: hidden;
}

.problem-image {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  display: block;
}

.cell-number {
  position: absolute;
  top: -8px;
  left: -6px;
  z-index: 3;
  display: grid;
  place-items: center;
  min-width: 20px;
  min-height: 20px;
  padding: 2px 4px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid rgba(154, 52, 18, 0.18);
  color: var(--accent-deep);
  font-size: 0.55rem;
  font-weight: 800;
  line-height: 1;
}

.cell-guides {
  position: absolute;
  inset: 0;
}

.guide {
  position: absolute;
  background: rgba(107, 114, 128, 0.35);
}

.guide.horizontal {
  left: 18px;
  right: 18px;
  top: 50%;
  height: 1px;
  transform: translateY(-50%);
}

.guide.vertical {
  top: 18px;
  bottom: 18px;
  left: 50%;
  width: 1px;
  transform: translateX(-50%);
}

.guide.dot {
  top: 50%;
  left: 50%;
  width: 8px;
  height: 8px;
  border-radius: 999px;
  transform: translate(-50%, -50%);
}

.pages.no-guides .cell-guides {
  display: none;
}

.pages.guide-horizontal .guide.vertical,
.pages.guide-horizontal .guide.dot {
  display: none;
}

.pages.guide-cross .guide.dot {
  display: none;
}

.pages.guide-dot .guide.horizontal,
.pages.guide-dot .guide.vertical {
  display: none;
}

@media (max-width: 900px) {
  .controls {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page {
    width: 100%;
    height: auto;
  }

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

  .cell {
    min-height: 260px;
  }

    .cell-toolbar {
      flex-wrap: wrap;
      max-width: calc(100% - 76px);
    }

  .field-wide {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  .app-shell {
    width: min(100vw - 20px, 100%);
    padding-top: 20px;
  }

  .hero,
  .page-header {
    flex-direction: column;
    align-items: start;
  }

  .hero-actions {
    width: 100%;
    display: grid;
    grid-template-columns: 1fr;
  }

  .hero-reset-button,
  .primary-button {
    width: 100%;
  }

  .page-signature {
    display: grid;
    gap: 8px;
    min-width: 0;
    width: 100%;
  }

  .page-meta {
    margin-top: 0;
    text-align: left;
  }

  .controls,
  .grid {
    grid-template-columns: 1fr;
  }

  .field-wide {
    grid-column: auto;
  }

  .page-info {
    display: grid;
    gap: 6px;
  }

  .page {
    width: 100%;
    padding: 20px;
  }

  .cell {
    min-height: 180px;
  }

  .pages.show-answers .cell {
    min-height: 260px;
  }

  .cell-toolbar {
    position: static;
    padding: 0 0 10px;
    max-width: none;
  }

  .cell-number {
    top: 0;
  }

  .cell-layout {
    inset: 14px;
    gap: 0;
  }
}

@media print {
  @page {
    size: A4 portrait;
    margin: 8mm;
  }

  body {
    background: white;
  }

  .app-shell {
    width: auto;
    padding: 0;
  }

  .hero,
  .controls,
  .primary-button {
    display: none;
  }

  .cell-toolbar {
    display: none;
  }

  .work-answer-toolbar {
    display: none;
  }

  .work-pane-body {
    grid-template-rows: minmax(0, 1fr);
  }

  .question-pane.has-question {
    padding-top: 0 !important;
  }

  .question-pane.has-question .cell-content {
    display: flex;
    align-items: flex-start;
    margin-top: 0 !important;
    padding-top: 0 !important;
    padding-left: 24px;
  }

  .question-pane.has-question .problem-text {
    padding-top: 0 !important;
    margin-top: 0 !important;
    align-self: flex-start;
  }

  .question-pane.has-question .problem-text > :first-child {
    margin-top: 0 !important;
  }

  .cell-layout {
    inset: 14px 16px;
  }

  .pages {
    margin: 0;
    gap: 0;
  }

  .page {
    width: 194mm;
    height: 281mm;
    min-height: 281mm;
    box-shadow: none;
    border-radius: 0;
    padding: 10mm;
    page-break-after: always;
  }

  .page-meta {
    margin-top: 6mm;
    text-align: center;
  }

  .page:last-child {
    page-break-after: auto;
  }

  .grid {
    gap: 10mm;
  }

  .cell {
    min-height: 0;
    break-inside: avoid;
  }
}