:root {
  --page: #f3f0e9;
  --surface: #ffffff;
  --surface-soft: #f8f6f1;
  --ink: #20251f;
  --muted: #5f665e;
  --line: #d8d8ce;
  --accent: #276749;
  --accent-dark: #1d4f38;
  --accent-soft: #e8f2eb;
  --danger: #9b332b;
  --danger-soft: #fbecea;
  --warning: #7b5316;
  --warning-soft: #fff5dd;
  --focus: #135fa7;
  --radius: 8px;
  font-family: Arial, Helvetica, sans-serif;
  color: var(--ink);
  background: var(--page);
  font-synthesis: none;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 0; line-height: 1.55; }
button, input, textarea { font: inherit; }
button, .button-label, a { -webkit-tap-highlight-color: transparent; }
button, .button-label {
  min-height: 44px;
  min-width: 44px;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: 0.58rem 0.9rem;
  background: var(--surface);
  color: var(--ink);
  font-weight: 700;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}
button:hover:not(:disabled), .button-label:hover { border-color: var(--accent); }
button.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
button.primary:hover:not(:disabled) { background: var(--accent-dark); }
button.secondary { color: var(--accent-dark); border-color: var(--accent); }
button.danger-button { color: var(--danger); border-color: var(--danger); }
button:disabled, fieldset:disabled button, fieldset:disabled textarea { cursor: not-allowed; opacity: 0.62; }
a { color: var(--accent-dark); text-underline-offset: 0.18em; }
a:focus-visible, button:focus-visible, input:focus-visible, textarea:focus-visible, .button-label:focus-within, [tabindex]:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
}
h1, h2, h3, h4, p { overflow-wrap: anywhere; }
h1, h2, h3, h4 { line-height: 1.2; margin-top: 0; }
h1 { font-size: clamp(1.85rem, 5vw, 3rem); letter-spacing: -0.035em; }
h2 { font-size: clamp(1.35rem, 3vw, 1.8rem); }
h3 { font-size: 1.12rem; }
p { margin-top: 0; }
[hidden] { display: none !important; }

.skip-link {
  position: fixed;
  z-index: 100;
  top: 0.5rem;
  left: 0.5rem;
  padding: 0.75rem 1rem;
  background: var(--ink);
  color: #fff;
  transform: translateY(-160%);
}
.skip-link:focus { transform: translateY(0); }
.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

.site-header { background: var(--surface); border-bottom: 1px solid var(--line); }
.header-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0.85rem 1.25rem;
  display: flex;
  align-items: center;
  gap: 1.25rem;
}
.wordmark { display: inline-flex; align-items: center; gap: 0.65rem; color: var(--ink); text-decoration: none; font-weight: 800; min-height: 44px; }
.wordmark-mark { display: grid; place-items: center; width: 42px; height: 42px; background: var(--accent); color: #fff; border-radius: 50%; font-family: "Courier New", monospace; }
.header-progress { margin-left: auto; min-width: 180px; font-size: 0.88rem; }
.header-progress span { display: block; margin-bottom: 0.25rem; }
progress { display: block; width: 100%; height: 0.65rem; accent-color: var(--accent); }
.header-actions { display: flex; gap: 0.5rem; }
.header-actions button, .header-actions .button-label { padding-inline: 0.75rem; }
#import-input:focus + * { outline: 3px solid var(--focus); }
.header-actions:has(#import-input:focus-visible) .button-label { outline: 3px solid var(--focus); outline-offset: 3px; }

.notice-band { background: var(--surface-soft); border-bottom: 1px solid var(--line); }
.notice-inner { max-width: 1280px; margin: 0 auto; padding: 0.55rem 1.25rem; display: flex; gap: 1rem; align-items: center; }
.notice-inner p { margin: 0; font-size: 0.83rem; }
.save-status { margin-left: auto !important; flex: 0 0 auto; font-weight: 700; color: var(--muted); }
.save-status[data-state="saved"] { color: var(--accent-dark); }
.save-status[data-state="unavailable"] { color: var(--danger); }
.storage-warning { max-width: 1232px; margin: 1rem auto 0; padding: 0.9rem 1rem; border: 1px solid var(--danger); background: var(--danger-soft); color: var(--ink); border-radius: var(--radius); }

main { max-width: 1280px; margin: 0 auto; padding: 2rem 1.25rem 3rem; }
.site-footer { max-width: 1280px; margin: 0 auto; padding: 1.5rem 1.25rem 2.5rem; border-top: 1px solid var(--line); color: var(--muted); font-size: 0.86rem; }
.site-footer p { max-width: 80ch; }
.eyebrow { color: var(--accent-dark); text-transform: uppercase; letter-spacing: 0.1em; font-size: 0.75rem; font-weight: 800; margin-bottom: 0.45rem; }
.lede { color: var(--muted); max-width: 68ch; font-size: 1.08rem; }
.muted { color: var(--muted); }
.small { font-size: 0.86rem; }
.inline-actions { display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center; }
.status-line { font-weight: 700; color: var(--muted); }
.status-line.complete { color: var(--accent-dark); }
.status-line.error { color: var(--danger); }

.overview-header { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 2rem; align-items: end; margin-bottom: 2rem; }
.overview-note { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 1rem; max-width: 330px; }
.overview-note p:last-child { margin-bottom: 0; }
.module-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.module-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 1.25rem; display: flex; flex-direction: column; min-width: 0; }
.module-card:hover { border-color: var(--accent); }
.module-card-top { display: flex; justify-content: space-between; gap: 0.75rem; align-items: flex-start; }
.module-number { color: var(--accent-dark); font-weight: 800; font-size: 0.82rem; text-transform: uppercase; letter-spacing: 0.06em; }
.module-card h2 { font-size: 1.3rem; margin-bottom: 0.45rem; }
.module-card p { color: var(--muted); }
.module-card .module-link { margin-top: auto; align-self: flex-start; min-height: 44px; display: inline-flex; align-items: center; font-weight: 700; }
.completion-badge { flex: 0 0 auto; border-radius: 999px; padding: 0.18rem 0.55rem; background: var(--surface-soft); color: var(--muted); font-size: 0.76rem; font-weight: 700; }
.completion-badge.complete { background: var(--accent-soft); color: var(--accent-dark); }

.workspace { display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: 1.5rem; align-items: start; }
.module-nav { position: sticky; top: 1rem; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 0.75rem; }
.module-nav h2 { font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.08em; margin: 0.35rem 0.5rem 0.65rem; }
.module-nav ol { list-style: none; padding: 0; margin: 0; }
.module-nav a { display: grid; grid-template-columns: 1.6rem minmax(0, 1fr); gap: 0.35rem; padding: 0.58rem 0.45rem; min-height: 44px; color: var(--ink); text-decoration: none; border-radius: 5px; font-size: 0.85rem; line-height: 1.3; align-items: center; }
.module-nav a[aria-current="page"] { background: var(--accent-soft); color: var(--accent-dark); font-weight: 800; }
.module-nav a:hover { background: var(--surface-soft); }
.module-nav .nav-state { grid-column: 2; font-size: 0.72rem; color: var(--muted); }
.module-content { min-width: 0; }
.module-heading { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: clamp(1rem, 3vw, 1.75rem); margin-bottom: 1rem; }
.module-heading h1 { margin-bottom: 0.5rem; }
.module-meta { display: flex; flex-wrap: wrap; gap: 0.6rem 1.25rem; color: var(--muted); font-size: 0.9rem; }
.concept-list { display: flex; flex-wrap: wrap; gap: 0.45rem; list-style: none; padding: 0; margin: 1rem 0 0; }
.concept-list li { background: var(--surface-soft); border: 1px solid var(--line); border-radius: 999px; padding: 0.25rem 0.65rem; font-size: 0.8rem; }
.stage-list { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0.5rem; margin-bottom: 1rem; }
.stage-jump { width: 100%; height: 100%; min-height: 52px; justify-content: flex-start; text-align: left; padding: 0.5rem 0.65rem; font-size: 0.8rem; }
.stage-jump span { display: block; font-size: 0.7rem; font-weight: 400; color: var(--muted); }
.stage-jump[data-complete="true"] { border-color: var(--accent); background: var(--accent-soft); }

.learning-section { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: clamp(1rem, 3vw, 1.5rem); margin-bottom: 1rem; scroll-margin-top: 1rem; min-width: 0; }
.learning-section.locked { background: var(--surface-soft); }
.section-heading { display: flex; gap: 1rem; justify-content: space-between; align-items: flex-start; margin-bottom: 1rem; }
.section-heading h2 { margin-bottom: 0.25rem; }
.section-heading p { margin-bottom: 0; }
.section-state { flex: 0 0 auto; font-size: 0.78rem; font-weight: 800; color: var(--muted); }
.section-state.complete { color: var(--accent-dark); }
.lock-message { padding: 0.75rem; background: var(--warning-soft); color: var(--warning); border-left: 3px solid var(--warning); }
fieldset { border: 0; padding: 0; margin: 0; min-width: 0; }
legend { font-weight: 800; margin-bottom: 0.65rem; padding: 0; }
label.field-label { display: block; font-weight: 700; margin: 0.8rem 0 0.35rem; }
.field-help { color: var(--muted); font-size: 0.88rem; margin-bottom: 0.7rem; }
textarea {
  display: block;
  width: 100%;
  max-width: 100%;
  min-height: 104px;
  resize: vertical;
  border: 1px solid #a8aca4;
  border-radius: 5px;
  background: var(--surface);
  color: var(--ink);
  padding: 0.75rem;
  line-height: 1.5;
}
textarea.code-editor, pre, code, .code-state { font-family: "Courier New", Courier, monospace; }
textarea.code-editor { min-height: 210px; tab-size: 4; white-space: pre; overflow: auto; }
textarea[aria-invalid="true"] { border-color: var(--danger); }
pre {
  margin: 0.5rem 0;
  padding: 0.8rem;
  max-width: 100%;
  overflow: auto;
  white-space: pre;
  background: #f5f5f1;
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 5px;
  line-height: 1.45;
  tab-size: 4;
}
.output-panel { border-top: 1px solid var(--line); margin-top: 1rem; padding-top: 1rem; min-width: 0; }
.output-panel h4 { margin-bottom: 0.35rem; }
.output-panel pre { max-height: 320px; }
.error-text { color: var(--danger); font-weight: 700; }
.success-text { color: var(--accent-dark); font-weight: 700; }
.expected-output { background: var(--surface-soft); }
.activity-card { border: 1px solid var(--line); border-radius: var(--radius); padding: 1rem; margin-top: 1rem; min-width: 0; }
.activity-card h3 { margin-bottom: 0.5rem; }
.radio-option { display: flex; gap: 0.65rem; align-items: flex-start; border: 1px solid var(--line); border-radius: 5px; padding: 0.65rem; margin: 0.5rem 0; min-height: 44px; cursor: pointer; }
.radio-option:has(input:checked) { border-color: var(--accent); background: var(--accent-soft); }
.radio-option input { width: 20px; height: 20px; flex: 0 0 auto; margin: 0.15rem 0 0; }
.model-answer, .explanation { border-left: 3px solid var(--accent); background: var(--accent-soft); padding: 0.75rem 1rem; margin-top: 0.75rem; }
.feedback { margin-top: 0.75rem; padding: 0.75rem; border: 1px solid var(--line); border-radius: 5px; }
.feedback.error { background: var(--danger-soft); border-color: var(--danger); }
.trace-controls { display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center; margin: 0.8rem 0; }
.trace-step { border: 1px solid var(--line); border-radius: 5px; padding: 1rem; }
.trace-layout { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.75rem; }
.runtime-bar { display: flex; align-items: center; flex-wrap: wrap; gap: 0.6rem; padding: 0.75rem; margin: 1rem 0; border: 1px solid var(--line); border-radius: 5px; background: var(--surface-soft); }
.runtime-bar p { margin: 0; }
.debug-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 1rem; }
.test-list { list-style: none; padding: 0; margin: 0.75rem 0; }
.test-list li { border-top: 1px solid var(--line); padding: 0.75rem 0; }
.test-result { font-weight: 800; }
.test-result.pass { color: var(--accent-dark); }
.test-result.fail { color: var(--danger); }
.completion-panel { border: 2px solid var(--accent); background: var(--accent-soft); padding: 1rem; border-radius: var(--radius); }
.reset-row { display: flex; flex-wrap: wrap; gap: 0.6rem; justify-content: space-between; border-top: 1px solid var(--line); padding-top: 1rem; margin-top: 1.5rem; }

dialog { width: min(560px, calc(100% - 2rem)); max-height: calc(100vh - 2rem); border: 1px solid var(--line); border-radius: var(--radius); padding: 0; color: var(--ink); background: var(--surface); }
dialog::backdrop { background: rgba(32, 37, 31, 0.55); }
.dialog-body { padding: 1.5rem; }
.dialog-actions { display: flex; justify-content: flex-end; flex-wrap: wrap; gap: 0.65rem; margin-top: 1.5rem; }
.noscript-message { margin: 2rem; padding: 1rem; background: var(--danger-soft); }

@media (max-width: 900px) {
  .header-inner { flex-wrap: wrap; gap: 0.65rem 1rem; }
  .header-progress { order: 3; flex: 1 0 100%; }
  .workspace { grid-template-columns: minmax(0, 1fr); }
  .module-nav { position: static; overflow-x: auto; padding: 0.5rem; }
  .module-nav h2 { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0, 0, 0, 0); }
  .module-nav ol { display: flex; gap: 0.35rem; width: max-content; }
  .module-nav li { width: 168px; }
  .module-nav a { border: 1px solid var(--line); height: 100%; }
  .stage-list { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}

@media (max-width: 600px) {
  main { padding: 1.25rem 0.75rem 2rem; }
  .header-inner, .notice-inner { padding-inline: 0.75rem; }
  .notice-inner { align-items: flex-start; }
  .notice-inner p:first-child { max-width: 42ch; }
  .overview-header { grid-template-columns: minmax(0, 1fr); gap: 1rem; }
  .overview-note { max-width: none; }
  .module-grid { grid-template-columns: minmax(0, 1fr); }
  .stage-list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .section-heading { display: block; }
  .section-state { display: block; margin-top: 0.5rem; }
  .trace-layout, .debug-grid { grid-template-columns: minmax(0, 1fr); }
  .storage-warning { margin-inline: 0.75rem; }
  .site-footer { padding-inline: 0.75rem; }
}

@media (max-width: 360px) {
  .wordmark { font-size: 0.95rem; }
  .wordmark-mark { width: 36px; height: 36px; }
  .header-actions { gap: 0.35rem; }
  .header-actions button, .header-actions .button-label { padding-inline: 0.55rem; }
  .save-status { font-size: 0.75rem !important; }
  .learning-section, .activity-card { padding: 0.8rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
}