:root {
  color-scheme: light;
  --accent: #ff6b35;
  --accent-soft: #ffe8de;
  --blue: #1b4d5c;
  --blue-deep: #102f3a;
  --canvas: #f6f3ec;
  --ink: #17272e;
  --muted: #5c6a70;
  --line: #d8d3c6;
  --panel: #fffdf8;
  --smooth: #2f7d5b;
  --smooth-soft: #e2f2ea;
  --shadow: 0 12px 34px rgba(17, 44, 52, 0.09);
  --radius: 16px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--canvas);
  color: var(--ink);
  font-family: Pretendard, "Noto Sans KR", "Apple SD Gothic Neo", system-ui, sans-serif;
  font-size: 18px;
  line-height: 1.7;
  -webkit-text-size-adjust: 100%;
}

/* readability: comfortable single column on every viewport */
.guide-header,
.guide-main,
.guide-footer {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 20px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: #fff;
  padding: 10px 16px;
  border-radius: 0 0 8px 0;
  z-index: 20;
}
.skip-link:focus {
  left: 0;
}

a {
  color: var(--blue);
}

/* ---- header ---- */
.guide-header {
  padding-top: 24px;
  padding-bottom: 8px;
}
.header-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.brand {
  margin: 0;
  font-size: 1.5rem;
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--blue-deep);
}
.brand-sub {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 1rem;
}
.mode-toggle label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--muted);
  cursor: pointer;
  padding: 8px 12px;
  border: 1.5px solid var(--line);
  border-radius: 999px;
  background: var(--panel);
}
.mode-toggle input {
  width: 18px;
  height: 18px;
  accent-color: var(--blue);
}
body.teacher-mode .mode-toggle label {
  border-color: var(--blue);
  color: var(--blue-deep);
  background: #e8f0f2;
}

/* ---- main ---- */
.guide-main {
  padding-top: 12px;
  padding-bottom: 40px;
  min-height: 50vh;
  outline: none;
}
.load-state,
.load-error {
  padding: 40px 0;
  color: var(--muted);
  font-size: 1.05rem;
}
.load-error {
  color: var(--accent);
  font-weight: 600;
}

/* ---- home: grade picker ---- */
.home-question {
  font-size: 1.9rem;
  line-height: 1.35;
  margin: 18px 0 8px;
  letter-spacing: -0.01em;
}
.home-help {
  color: var(--muted);
  margin: 0 0 20px;
}
.grade-group {
  margin-bottom: 22px;
}
.grade-group-title {
  font-size: 1.05rem;
  color: var(--muted);
  margin: 0 0 10px;
  font-weight: 700;
}
.grade-buttons {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}
.grade-btn {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 6px;
  padding: 16px;
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  cursor: pointer;
  text-align: left;
  font: inherit;
  color: var(--ink);
  transition: border-color 0.15s, transform 0.15s, box-shadow 0.15s;
}
.grade-btn:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}
.grade-btn.is-transition {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.grade-btn-label {
  font-size: 1.1rem;
  font-weight: 700;
}
.grade-btn-tag {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--muted);
}
.grade-btn.is-transition .grade-btn-tag {
  color: var(--accent);
}

/* ---- grade screen ---- */
.back-bar {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  margin: 8px 0 18px;
}
.back-btn,
.preview-link {
  font: inherit;
  font-weight: 700;
  color: var(--blue);
  background: none;
  border: 1.5px solid var(--line);
  border-radius: 999px;
  padding: 8px 14px;
  cursor: pointer;
}
.back-btn:hover,
.preview-link:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.crumb {
  color: var(--muted);
  font-weight: 600;
}
.grade-kicker {
  margin: 0;
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 0.01em;
}
.grade-headline {
  font-size: 1.75rem;
  line-height: 1.35;
  margin: 6px 0 10px;
}
.grade-summary {
  font-size: 1.1rem;
  margin: 0 0 12px;
}
.subject-count-note {
  color: var(--muted);
  margin: 0 0 18px;
}

.upcoming-card {
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  padding: 20px;
  margin-top: 12px;
}
.upcoming-card h2 {
  margin: 0 0 6px;
  font-size: 1.2rem;
}
.preview-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 12px;
}

/* ---- subject cards ---- */
.subject-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.subject {
  border: 1.5px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  overflow: hidden;
}
.subject.is-smooth {
  background: var(--smooth-soft);
  border-color: #b7ddca;
}
.subject-summary {
  cursor: pointer;
  padding: 18px 20px;
  list-style: none;
}
.subject-summary::-webkit-details-marker {
  display: none;
}
.subject-summary::after {
  content: "펼치기 ▾";
  float: right;
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 700;
}
.subject[open] .subject-summary::after {
  content: "접기 ▴";
}
.subject-title-row {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.subject-name {
  font-size: 1.25rem;
  font-weight: 800;
}
.badges {
  display: inline-flex;
  gap: 6px;
  flex-wrap: wrap;
}
.badge {
  font-size: 0.78rem;
  font-weight: 700;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: #b4431c;
}
.badge-smooth {
  background: #cdeadd;
  color: var(--smooth);
}
.subject-lead {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 1rem;
}
.subject.is-smooth .subject-lead {
  color: #2f6a52;
}

.subject-body {
  padding: 4px 20px 22px;
  border-top: 1px dashed var(--line);
}
.subject-intro {
  font-size: 1.05rem;
  margin: 16px 0 0;
}
.sub-block,
.field-signal,
.new-concepts {
  margin-top: 20px;
}
.section-h {
  font-size: 1.1rem;
  margin: 0 0 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.sub-block p,
.field-signal p {
  margin: 0 0 8px;
}
.ai-tag {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  border: 1px solid var(--accent);
  border-radius: 999px;
  padding: 1px 8px;
}

.field-signal {
  background: #f3eefa;
  border: 1px solid #d9c9ef;
  border-radius: 12px;
  padding: 14px 16px;
}
.field-caveat {
  color: #6a4b93;
  font-size: 0.92rem;
  margin-bottom: 0 !important;
}

/* ---- new concepts ---- */
.new-concepts-help {
  color: var(--muted);
  margin: 0 0 12px;
  font-size: 0.98rem;
}
.concept-domain {
  margin-bottom: 14px;
}
.concept-domain-title {
  font-size: 1rem;
  margin: 0 0 6px;
  color: var(--blue-deep);
}
.concept-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.concept-item {
  border-left: 3px solid var(--accent-soft);
  padding-left: 12px;
}
.concept-label {
  margin: 0;
  font-weight: 700;
  display: flex;
  align-items: baseline;
  gap: 8px;
  flex-wrap: wrap;
}
.concept-explain {
  margin: 2px 0 0;
  color: var(--muted);
  font-size: 0.98rem;
}

/* code chips: hidden until 교사 모드 */
.code-chip {
  display: none;
  font-size: 0.75rem;
  font-weight: 700;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  color: var(--blue);
  background: #e8f0f2;
  border-radius: 6px;
  padding: 1px 6px;
}
body.teacher-mode .code-chip {
  display: inline-block;
}

/* ---- evidence fold ---- */
.evidence {
  margin-top: 20px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #faf8f2;
}
.evidence > summary {
  cursor: pointer;
  padding: 12px 16px;
  font-weight: 700;
  color: var(--blue);
  font-size: 0.95rem;
}
.evidence-body {
  padding: 4px 16px 16px;
  font-size: 0.95rem;
}
.evidence-facts {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 4px 16px;
  margin: 8px 0 0;
}
.evidence-facts dt {
  font-weight: 700;
  color: var(--muted);
}
.evidence-facts dd {
  margin: 0;
}
.evidence-sub {
  font-size: 0.95rem;
  margin: 14px 0 4px;
}
.evidence-rationale,
.evidence-basis {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
}
.evidence-rationale li,
.evidence-basis li {
  margin-bottom: 4px;
}

/* ---- footer ---- */
.guide-footer {
  border-top: 1px solid var(--line);
  padding-top: 18px;
  padding-bottom: 40px;
  color: var(--muted);
  font-size: 0.95rem;
}
.guide-footer p {
  margin: 0 0 8px;
}
.expert-link a {
  font-weight: 700;
}

/* ---- focus visibility (keyboard) ---- */
:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
  border-radius: 8px;
}

/* ---- responsive ---- */
@media (max-width: 520px) {
  body {
    font-size: 17px;
  }
  .grade-buttons {
    grid-template-columns: repeat(2, 1fr);
  }
  .home-question {
    font-size: 1.6rem;
  }
  .grade-headline {
    font-size: 1.5rem;
  }
}

/* ---- reduced motion ---- */
@media (prefers-reduced-motion: reduce) {
  * {
    scroll-behavior: auto !important;
    transition: none !important;
    animation: none !important;
  }
  .grade-btn:hover {
    transform: none;
  }
}

/* ---- print: one grade → clean A4 pages ---- */
@media print {
  body {
    background: #fff;
    font-size: 12pt;
    line-height: 1.5;
  }
  .guide-header .mode-toggle,
  .back-bar,
  .skip-link,
  .subject-summary::after,
  .preview-links,
  .expert-link {
    display: none !important;
  }
  .guide-header,
  .guide-main,
  .guide-footer {
    max-width: none;
    padding: 0;
  }
  /* force every fold open so the printout is complete */
  .subject[open],
  .subject {
    break-inside: avoid;
    page-break-inside: avoid;
    box-shadow: none;
    border: 1px solid #999;
  }
  .subject-body {
    display: block !important;
  }
  details:not([open]) > .subject-body,
  .evidence-body {
    display: block !important;
  }
  .code-chip {
    display: inline-block !important;
  }
  .subject-summary::after {
    content: "";
  }
  .guide-footer {
    border-top: 1px solid #999;
    color: #333;
  }
}