:root {
  --bg: #f6f8fb;
  --panel: #ffffff;
  --panel-alt: #f8fafc;
  --text: #0f172a;
  --muted: #475569;
  --border: #dbe4ef;
  --accent: #2563eb;
  --accent-soft: #dbeafe;
  --success: #0f766e;
  --warning: #b45309;
  --danger: #b91c1c;
  --shadow: 0 12px 32px rgba(15, 23, 42, 0.08);
  --radius: 18px;
  --radius-sm: 12px;
  --max-width: 1200px;
  --line: 1.8;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.08), transparent 28%),
    linear-gradient(180deg, #f8fbff 0%, var(--bg) 30%, var(--bg) 100%);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans", "Yu Gothic", "Meiryo", sans-serif;
  line-height: var(--line);
}

img {
  max-width: 100%;
  height: auto;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

code,
pre {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
}

code {
  background: #eff6ff;
  color: #1d4ed8;
  border: 1px solid #dbeafe;
  border-radius: 8px;
  padding: 0.1rem 0.4rem;
  font-size: 0.95em;
}

pre {
  background: #0f172a;
  color: #e2e8f0;
  border-radius: 18px;
  padding: 18px 20px;
  overflow: auto;
  line-height: 1.65;
  box-shadow: 0 16px 40px rgba(15, 23, 42, 0.22);
}

pre code {
  background: transparent;
  color: inherit;
  border: none;
  padding: 0;
}

h1,
h2,
h3,
h4 {
  line-height: 1.25;
  letter-spacing: 0.01em;
  margin: 0 0 0.7em;
}

h1 {
  font-size: clamp(2rem, 4vw, 3.25rem);
}

h2 {
  font-size: clamp(1.35rem, 2.2vw, 1.9rem);
  margin-top: 1.8em;
}

h3 {
  font-size: 1.1rem;
  margin-top: 1.4em;
}

p,
ul,
ol,
blockquote,
table,
figure {
  margin: 0 0 1.1rem;
}

ul,
ol {
  padding-left: 1.3rem;
}

li + li {
  margin-top: 0.35rem;
}

blockquote {
  margin: 1.2rem 0;
  padding: 1rem 1.2rem;
  border-left: 4px solid var(--accent);
  background: linear-gradient(135deg, #eff6ff, #ffffff);
  border-radius: 0 14px 14px 0;
  color: #1e3a8a;
}

hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 2rem 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: #fff;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: var(--shadow);
}

th,
td {
  padding: 0.9rem 1rem;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--border);
}

tr:last-child td {
  border-bottom: none;
}

th {
  background: #f8fafc;
  font-weight: 700;
}

.table-wrap {
  overflow-x: auto;
  border-radius: 16px;
}

.muted {
  color: var(--muted);
}

.small {
  font-size: 0.95rem;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.28rem 0.7rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: #1d4ed8;
  font-weight: 700;
  font-size: 0.84rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin: 1rem 0 1.4rem;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  background: #eef2ff;
  color: #3730a3;
  font-weight: 600;
  font-size: 0.88rem;
}

.shell-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.95);
  border-bottom: 1px solid rgba(219, 228, 239, 0.9);
}

.shell-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.95rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.7rem 1.2rem;
}

.brand {
  font-weight: 800;
  color: var(--text);
}

.brand:hover {
  text-decoration: none;
}

.breadcrumbs {
  font-size: 0.92rem;
  color: var(--muted);
}

.breadcrumbs a {
  color: var(--muted);
}

.page {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 1.8rem 1.25rem 3rem;
  display: grid;
  grid-template-columns: minmax(260px, 280px) minmax(0, 1fr);
  gap: 1.6rem 2rem;
  align-items: start;
}

.page--single {
  grid-template-columns: 1fr;
}

.sidebar {
  position: sticky;
  top: 5.4rem;
}

.card,
.sidebar-card,
.lesson-card,
.figure-card,
.quiz-card,
.sim-card,
.course-card,
.notice-card,
.metric-card {
  background: var(--panel);
  border: 1px solid rgba(219, 228, 239, 0.92);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.sidebar-card,
.lesson-card,
.figure-card,
.quiz-card,
.sim-card,
.notice-card,
.metric-card {
  padding: 1.25rem;
}

.lesson-card + .lesson-card {
  margin-top: 1rem;
}

.lesson {
  min-width: 0;
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(320px, 0.85fr);
  gap: 1.25rem;
  align-items: stretch;
}

.hero-copy,
.hero-visual {
  background: linear-gradient(180deg, rgba(255,255,255,0.98), rgba(255,255,255,0.92));
  border: 1px solid rgba(219, 228, 239, 0.92);
  border-radius: 26px;
  box-shadow: var(--shadow);
  padding: 1.45rem;
}

.hero-copy h1 {
  margin-bottom: 0.3rem;
}

.lead {
  font-size: 1.08rem;
  color: #1e293b;
  margin-bottom: 1rem;
}

.metric-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 0.8rem;
  margin: 1rem 0 1.2rem;
}

.metric-card {
  padding: 0.95rem;
}

.metric-label {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 0.25rem;
}

.metric-value {
  font-size: 1rem;
  font-weight: 700;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
}

.button {
  appearance: none;
  border: none;
  cursor: pointer;
  background: var(--accent);
  color: #fff;
  padding: 0.86rem 1.1rem;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.95rem;
  box-shadow: 0 10px 25px rgba(37, 99, 235, 0.22);
}

.button:hover {
  text-decoration: none;
  filter: brightness(1.03);
}

.button--ghost {
  background: #fff;
  color: var(--text);
  border: 1px solid var(--border);
  box-shadow: none;
}

.button[hidden] {
  display: none !important;
}

.course-nav {
  display: grid;
  gap: 0.45rem;
  margin-top: 1rem;
}

.course-nav-link {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.8rem;
  padding: 0.8rem 0.9rem;
  border-radius: 12px;
  background: #f8fafc;
  color: var(--text);
  border: 1px solid rgba(219, 228, 239, 0.8);
  transition: transform 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}

.course-nav-link:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.course-nav-link .course-nav-meta {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  font-size: 0.78rem;
  color: var(--muted);
  white-space: nowrap;
}

.course-nav-link.is-current {
  background: linear-gradient(135deg, #2563eb, #1d4ed8);
  color: #fff;
  border-color: rgba(37, 99, 235, 0.8);
}

.course-nav-link.is-current .course-nav-meta {
  color: rgba(255,255,255,0.8);
}

.course-nav-link.is-visited:not(.is-current) {
  background: linear-gradient(135deg, #ecfeff, #f8fafc);
}

.course-nav-link.is-visited .course-nav-meta::before {
  content: "Viewed";
  color: var(--success);
  font-weight: 700;
}

.progress-wrap {
  margin-top: 1rem;
}

.progress-bar {
  height: 10px;
  border-radius: 999px;
  background: #e2e8f0;
  overflow: hidden;
}

.progress-fill {
  display: block;
  height: 100%;
  width: 0%;
  border-radius: inherit;
  background: linear-gradient(90deg, #60a5fa, #2563eb);
  transition: width 0.25s ease;
}

.progress-text {
  margin-top: 0.45rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.lesson-header {
  margin-bottom: 1rem;
}

.chapter-kicker {
  display: block;
  color: var(--accent);
  font-weight: 800;
  margin-bottom: 0.3rem;
}

.lesson-summary {
  font-size: 1.05rem;
  color: #334155;
  margin-bottom: 1rem;
}

.figure-card {
  overflow: hidden;
}

.figure-card img {
  display: block;
  width: 100%;
  border-radius: 14px;
  background: #fff;
}

.figure-caption {
  font-size: 0.92rem;
  color: var(--muted);
  margin-top: 0.8rem;
}

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

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

.notice-card {
  border-left: 5px solid var(--accent);
  background: linear-gradient(135deg, #eff6ff, #ffffff);
}

.lesson-links {
  display: grid;
  gap: 0.8rem;
  margin-top: 1.1rem;
}

.lesson-link {
  display: block;
  padding: 1rem 1.1rem;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: #fff;
  color: var(--text);
  box-shadow: var(--shadow);
}

.lesson-link:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.lesson-link strong {
  display: block;
  margin-bottom: 0.2rem;
}

.course-list-grid {
  display: grid;
  gap: 1rem;
}

.course-card {
  padding: 1.25rem;
  color: var(--text);
  display: block;
}

.course-card:hover {
  text-decoration: none;
  transform: translateY(-2px);
}

.course-card h2 {
  margin-top: 0.35rem;
  margin-bottom: 0;
}

.course-card p,
.course-card .course-meta,
.course-card .chapter-mini {
  display: none;
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  margin-top: 1.8rem;
}

.footer-nav a {
  flex: 1;
  min-width: 230px;
  padding: 1rem 1.05rem;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: #fff;
  color: var(--text);
  box-shadow: var(--shadow);
}

.footer-nav a:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.footer-nav strong {
  display: block;
  margin-bottom: 0.15rem;
}

.site-footer {
  max-width: var(--max-width);
  margin: 0 auto 3rem;
  padding: 0 1.25rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.site-footer .card {
  padding: 1rem 1.2rem;
}

.rule-table td:first-child,
.rule-table th:first-child {
  white-space: nowrap;
}

.rule-pill {
  display: inline-flex;
  align-items: center;
  border-radius: 999px;
  padding: 0.2rem 0.55rem;
  font-size: 0.82rem;
  font-weight: 700;
  background: #eff6ff;
  color: #1d4ed8;
}

.sim-shell {
  display: grid;
  gap: 1rem;
}

.sim-controls {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1rem;
}

.control-group {
  background: #f8fafc;
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 1rem;
}

.control-label {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  font-weight: 700;
  margin-bottom: 0.55rem;
}

.control-value {
  color: var(--accent);
  font-size: 1.1rem;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--accent);
}

.preset-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.preset-button {
  appearance: none;
  border: 1px solid var(--border);
  background: #fff;
  color: var(--text);
  border-radius: 999px;
  padding: 0.45rem 0.8rem;
  cursor: pointer;
  font-weight: 600;
}

.sim-output-grid {
  display: grid;
  grid-template-columns: minmax(280px, 0.9fr) minmax(0, 1.1fr);
  gap: 1rem;
}

.readout-stack {
  display: grid;
  gap: 0.8rem;
}

.output-readout {
  background: linear-gradient(135deg, #eff6ff, #ffffff);
  border: 1px solid #dbeafe;
  border-radius: 18px;
  padding: 1rem;
}

.output-main {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  line-height: 1;
  margin-bottom: 0.35rem;
}

.output-sub {
  color: var(--muted);
}

.compare-row {
  display: grid;
  gap: 0.75rem;
}

.compare-item {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.75rem 0.9rem;
  border-radius: 14px;
  background: #f8fafc;
  border: 1px solid var(--border);
}

.compare-item strong {
  color: var(--text);
}

.svg-panel {
  border-radius: 16px;
  border: 1px solid var(--border);
  background: #fff;
  overflow: hidden;
}

.rule-list {
  display: grid;
  gap: 0.7rem;
}

.rule-row {
  padding: 0.85rem 0.95rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: #fff;
}

.rule-row strong {
  display: block;
  margin-bottom: 0.35rem;
}

.rule-bar {
  height: 10px;
  border-radius: 999px;
  background: #e2e8f0;
  overflow: hidden;
  margin-top: 0.55rem;
}

.rule-bar span {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, #60a5fa, #2563eb);
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem 1rem;
  margin-top: 0.75rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.legend span {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}

.legend i {
  display: inline-block;
  width: 14px;
  height: 14px;
  border-radius: 999px;
}

.legend .legend-fuzzy { background: #2563eb; }
.legend .legend-threshold { background: #64748b; }
.legend .legend-agg { background: rgba(37,99,235,0.18); border: 1px solid #93c5fd; }
.legend .legend-centroid { background: #b45309; }

.quiz-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-top: 1.2rem;
}

.quiz-result {
  padding: 1rem 1.1rem;
  border-radius: 16px;
  border: 1px solid var(--border);
  background: linear-gradient(135deg, #eff6ff, #ffffff);
  margin-bottom: 1rem;
}

.quiz-result strong {
  font-size: 1.05rem;
}

.quiz-list {
  display: grid;
  gap: 1rem;
}

.quiz-question {
  border: 1px solid var(--border);
  border-radius: 18px;
  background: #fff;
  overflow: hidden;
}

.quiz-question-header {
  padding: 1rem 1.1rem 0;
}

.quiz-question-body {
  padding: 0 1.1rem 1.1rem;
}

.quiz-option {
  display: block;
  padding: 0.85rem 0.95rem;
  border: 1px solid var(--border);
  border-radius: 14px;
  margin-top: 0.7rem;
  cursor: pointer;
  transition: border-color 0.15s ease, background 0.15s ease;
}

.quiz-option:hover {
  background: #f8fafc;
}

.quiz-option input {
  margin-right: 0.55rem;
}

.quiz-option.is-correct {
  border-color: rgba(15, 118, 110, 0.6);
  background: rgba(240, 253, 250, 1);
}

.quiz-option.is-wrong {
  border-color: rgba(185, 28, 28, 0.45);
  background: rgba(254, 242, 242, 1);
}

.quiz-feedback {
  margin-top: 0.8rem;
  padding: 0.85rem 0.95rem;
  border-radius: 14px;
  background: #f8fafc;
  border: 1px solid var(--border);
}

.quiz-feedback.is-correct {
  border-color: rgba(15, 118, 110, 0.45);
  background: rgba(240, 253, 250, 1);
}

.quiz-feedback.is-wrong {
  border-color: rgba(185, 28, 28, 0.35);
  background: rgba(254, 242, 242, 1);
}

.kv-list {
  display: grid;
  gap: 0.8rem;
}

.kv-item {
  padding: 0.95rem 1rem;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: #fff;
}

.kv-item strong {
  display: block;
  margin-bottom: 0.25rem;
}

.callout-grid {
  display: grid;
  gap: 1rem;
}

.note-list {
  display: grid;
  gap: 0.8rem;
}

.note-item {
  display: grid;
  gap: 0.25rem;
  padding: 0.95rem 1rem;
  border-radius: 14px;
  background: #fff;
  border: 1px solid var(--border);
}

.pill-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.pill-list span {
  display: inline-flex;
  padding: 0.28rem 0.65rem;
  border-radius: 999px;
  background: #f1f5f9;
  color: #334155;
  font-size: 0.86rem;
  font-weight: 600;
}

.caption {
  font-size: 0.92rem;
  color: var(--muted);
}

.no-js {
  padding: 1rem 1.1rem;
  border-radius: 14px;
  background: #fff7ed;
  border: 1px solid #fdba74;
  color: #9a3412;
}

@media (max-width: 1100px) {
  .metric-grid,
  .grid-3 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .hero-grid,
  .sim-output-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 920px) {
  .page {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    order: 2;
  }

  .lesson {
    order: 1;
  }
}

@media (max-width: 720px) {
  .metric-grid,
  .grid-2,
  .sim-controls {
    grid-template-columns: 1fr;
  }

  .shell-inner {
    padding-inline: 1rem;
  }

  .page,
  .site-footer {
    padding-inline: 1rem;
  }

  .hero-copy,
  .hero-visual,
  .lesson-card,
  .figure-card,
  .sidebar-card,
  .quiz-card,
  .sim-card,
  .notice-card,
  .metric-card,
  .course-card {
    padding: 1rem;
  }
}


/* FC101 v2 additions */
.equation-grid {
  display: grid;
  gap: 0.9rem;
}

.equation-card {
  padding: 1rem 1.05rem;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: #fff;
}

.equation-card strong {
  display: block;
  margin-bottom: 0.3rem;
}

.table-note {
  font-size: 0.92rem;
  color: var(--muted);
  margin-top: 0.75rem;
}

.summary-table td code,
.summary-table th code {
  white-space: nowrap;
}

.practice-card {
  display: grid;
  gap: 1rem;
}

.practice-header {
  display: grid;
  gap: 0.55rem;
}

.practice-header h2 {
  margin: 0;
}

.practice-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
}

.practice-meta span {
  display: inline-flex;
  align-items: center;
  padding: 0.28rem 0.65rem;
  border-radius: 999px;
  background: #f1f5f9;
  color: #334155;
  font-size: 0.86rem;
  font-weight: 600;
}

.practice-question {
  border: 1px solid var(--border);
  border-radius: 18px;
  background: #fff;
  overflow: hidden;
}

.practice-question-header {
  padding: 1rem 1.1rem 0;
}

.practice-question-body {
  padding: 0 1.1rem 1.1rem;
}

.practice-input-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 0.8rem;
}

.practice-input {
  width: min(260px, 100%);
  appearance: none;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 0.8rem 0.9rem;
  font-size: 1rem;
  background: #fff;
  color: var(--text);
}

.practice-input:focus {
  outline: 2px solid rgba(37, 99, 235, 0.14);
  border-color: rgba(37, 99, 235, 0.55);
}

.practice-input.is-correct {
  border-color: rgba(15, 118, 110, 0.6);
  background: rgba(240, 253, 250, 1);
}

.practice-input.is-wrong {
  border-color: rgba(185, 28, 28, 0.45);
  background: rgba(254, 242, 242, 1);
}

.practice-unit {
  color: var(--muted);
  font-weight: 600;
}

.practice-status {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  font-weight: 700;
}

.practice-status.is-passed {
  color: var(--success);
}

.practice-status.is-pending {
  color: var(--warning);
}

.snapshot-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.75rem;
  margin-top: 0.75rem;
}

.snapshot-item {
  padding: 0.85rem 0.9rem;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: #fff;
}

.snapshot-item strong {
  display: block;
  margin-bottom: 0.15rem;
}

.summary-mini-table td,
.summary-mini-table th {
  padding: 0.65rem 0.8rem;
  font-size: 0.94rem;
}

@media (max-width: 1100px) {
  .snapshot-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 720px) {
  .snapshot-grid {
    grid-template-columns: 1fr;
  }
}