:root {
  --bg: #f7f1e8;
  --fg: #1e1a16;
  --muted: #5e544c;
  --accent: #c65a2e;
  --accent-2: #2f6f6a;
  --danger: #b33a3a;
  --border: #d8cabb;
  --panel: #fff7ed;
  --code-bg: #191816;
  --code-fg: #f6e9da;
  --highlight: #ffd166;
  --shadow: rgba(24, 19, 14, 0.12);
  --cell-size: 2.6rem;
}

body[data-contrast="high"] {
  --bg: #ffffff;
  --fg: #000000;
  --muted: #111111;
  --accent: #0033cc;
  --accent-2: #006400;
  --danger: #990000;
  --border: #000000;
  --panel: #ffffff;
  --code-bg: #000000;
  --code-fg: #ffffff;
  --highlight: #ffbf00;
  --shadow: rgba(0, 0, 0, 0.4);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Iowan Old Style", "Palatino Linotype", "Bookman Old Style", "Garamond", serif;
  color: var(--fg);
  background: radial-gradient(circle at top left, #fbe9d3 0%, transparent 55%),
    radial-gradient(circle at 30% 20%, rgba(47, 111, 106, 0.12), transparent 50%), var(--bg);
  line-height: 1.6;
}

main {
  padding: 0 1.5rem 4rem;
}

article {
  max-width: 1150px;
  margin: 0 auto;
}

h1,
h2,
h3 {
  font-family: "Bodoni MT", "Didot", "Palatino Linotype", serif;
  letter-spacing: 0.02em;
  margin-top: 2.2rem;
  color: var(--fg);
}

h1 {
  font-size: clamp(2.6rem, 4vw, 3.6rem);
  margin: 0.4rem 0 1rem;
}

h2 {
  font-size: clamp(1.7rem, 3vw, 2.3rem);
}

h3 {
  font-size: 1.1rem;
  margin: 0;
}

p {
  margin: 0.5rem 0 1rem;
}

a {
  color: var(--accent-2);
}

a:hover {
  color: var(--accent);
}

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

.hero {
  padding: 3.3rem 1.5rem 2.2rem;
  background: linear-gradient(120deg, rgba(198, 90, 46, 0.12), rgba(47, 111, 106, 0.12));
  border-bottom: 1px solid var(--border);
  position: relative;
  overflow: hidden;
}

.hero::after {
  content: "";
  position: absolute;
  top: -80px;
  right: -120px;
  width: 320px;
  height: 320px;
  background: radial-gradient(circle, rgba(198, 90, 46, 0.25), transparent 65%);
  z-index: 0;
}

.hero-inner {
  max-width: 1150px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.kicker {
  text-transform: uppercase;
  letter-spacing: 0.2em;
  font-size: 0.75rem;
  color: var(--muted);
  margin: 0;
}

.hero-controls {
  display: flex;
  gap: 1rem;
  align-items: center;
  flex-wrap: wrap;
  margin-top: 1.5rem;
}

.toc {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 1rem;
  padding: 1.2rem 1.4rem;
  margin-top: 2rem;
  box-shadow: 0 12px 28px -20px var(--shadow);
}

.toc ol {
  columns: 2;
  column-gap: 2rem;
  padding-left: 1.2rem;
}

.toc li {
  break-inside: avoid;
  margin-bottom: 0.4rem;
}

.toggle {
  display: inline-flex;
  gap: 0.5rem;
  align-items: center;
  font-size: 0.9rem;
}

button,
select,
input[type="text"],
input[type="range"] {
  font-family: inherit;
  font-size: 0.95rem;
}

button {
  border: 1px solid var(--border);
  background: var(--accent);
  color: #fff;
  padding: 0.5rem 0.9rem;
  border-radius: 999px;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  box-shadow: 0 10px 20px -12px var(--shadow);
}

button:hover {
  transform: translateY(-1px);
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

button.ghost {
  background: transparent;
  color: var(--accent);
}

input[type="text"],
select {
  width: 100%;
  padding: 0.45rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: 0.5rem;
  background: var(--panel);
}

input[type="range"] {
  width: 140px;
}

label {
  display: grid;
  gap: 0.35rem;
  font-size: 0.95rem;
}

:focus-visible {
  outline: 3px solid var(--accent-2);
  outline-offset: 2px;
}

.plain-list {
  padding-left: 1.2rem;
}

.plain-list li {
  margin-bottom: 0.4rem;
}

.link-out {
  font-size: 0.95rem;
  color: var(--muted);
}

.matrix-figure {
  background: var(--panel);
  padding: 1rem;
  border-radius: 1rem;
  border: 1px solid var(--border);
  box-shadow: 0 12px 26px -18px var(--shadow);
  margin: 1.5rem 0;
}

.matrix-figure table {
  width: 100%;
  border-collapse: collapse;
  text-align: center;
}

.matrix-figure th,
.matrix-figure td {
  border: 1px solid var(--border);
  padding: 0.4rem;
}

.formula {
  background: var(--panel);
  padding: 1rem 1.2rem;
  border-radius: 0.8rem;
  border: 1px solid var(--border);
  overflow-x: auto;
}

.concept-actions {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
  margin-top: 0.8rem;
}

.svg-explainer figure {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 1rem;
  padding: 1rem;
  box-shadow: 0 10px 26px -18px var(--shadow);
}

.svg-explainer svg {
  width: 100%;
  height: auto;
}

.svg-explainer .grid rect {
  fill: #fff;
  stroke: var(--border);
  stroke-width: 2;
}

.svg-explainer .dep {
  fill: rgba(47, 111, 106, 0.25);
  animation: depPulse 3s infinite;
}

.svg-explainer .dep-b {
  animation-delay: 0.4s;
}

.svg-explainer .dep-c {
  animation-delay: 0.8s;
}

.svg-explainer .current-cell {
  fill: rgba(198, 90, 46, 0.35);
  stroke: var(--accent);
  stroke-width: 2;
  animation: currentPulse 3s infinite;
}

.svg-explainer .cursor {
  fill: var(--accent-2);
  animation: cursorMove 3s infinite;
}

.svg-explainer text {
  font-family: "SFMono-Regular", "Consolas", "Liberation Mono", "Menlo", monospace;
  font-size: 12px;
  fill: var(--muted);
}

.simulator {
  margin-top: 2.2rem;
  padding: 2rem;
  border-radius: 1.6rem;
  border: 1px solid var(--border);
  background: var(--panel);
  box-shadow: 0 18px 40px -24px var(--shadow);
  font-size: 1rem;
}

.sim-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  flex-wrap: wrap;
}

.sim-header-actions {
  display: grid;
  gap: 0.8rem;
}

.sim-hint {
  background: rgba(47, 111, 106, 0.1);
  border: 1px solid rgba(47, 111, 106, 0.3);
  padding: 0.6rem 0.8rem;
  border-radius: 0.8rem;
  font-size: 0.85rem;
}

.focus-toggle {
  display: inline-flex;
  gap: 0.4rem;
  align-items: center;
  flex-wrap: wrap;
  font-size: 0.85rem;
  color: var(--muted);
}

.focus-toggle button {
  padding: 0.35rem 0.7rem;
}

.focus-toggle button[aria-pressed="true"] {
  background: var(--accent-2);
  color: #fff;
  border-color: transparent;
}

.sim-essential {
  margin: 1.2rem 0 1rem;
  display: grid;
  gap: 0.8rem;
}

.input-row,
.control-row {
  display: grid;
  gap: 0.8rem;
}

.control-row {
  align-items: end;
}

.speed-control {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.warning {
  min-height: 1.2rem;
  color: var(--danger);
  font-size: 0.85rem;
}

.sim-advanced {
  border: 1px solid var(--border);
  border-radius: 1rem;
  padding: 0.8rem 1rem 1rem;
  background: rgba(255, 255, 255, 0.55);
}

.sim-advanced summary {
  cursor: pointer;
  font-weight: 600;
}

.advanced-grid {
  margin-top: 0.8rem;
  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  align-items: start;
}

fieldset {
  border: 1px solid var(--border);
  border-radius: 0.8rem;
  padding: 0.6rem 0.8rem;
  display: grid;
  gap: 0.4rem;
}

legend {
  font-size: 0.8rem;
  padding: 0 0.3rem;
  color: var(--muted);
}

.checkbox {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.advanced-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.advanced-dev {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px dashed var(--border);
}

#test-output {
  background: #111;
  color: #e2e2e2;
  padding: 0.8rem;
  border-radius: 0.6rem;
  overflow: auto;
  min-height: 3rem;
}

.sim-panes {
  margin-top: 1.5rem;
  display: grid;
  gap: 0;
  --code-width: minmax(280px, 1.2fr);
  --matrix-width: minmax(320px, 1.4fr);
  --watch-width: minmax(260px, 1fr);
  --splitter-width: 12px;
  grid-template-columns: var(--code-width) var(--splitter-width) var(--matrix-width) var(--splitter-width)
    var(--watch-width);
  align-items: stretch;
}

.pane {
  background: #fff;
  border-radius: 1rem;
  border: 1px solid var(--border);
  padding: 1rem;
  display: flex;
  flex-direction: column;
  min-height: 340px;
}

.pane-header {
  display: flex;
  justify-content: space-between;
  gap: 0.8rem;
  align-items: flex-start;
  margin-bottom: 0.8rem;
}

.pane-note {
  margin: 0.2rem 0 0;
  font-size: 0.85rem;
  color: var(--muted);
}

.code-block {
  margin: 0;
  padding: 0.8rem;
  background: var(--code-bg);
  color: var(--code-fg);
  border-radius: 0.8rem;
  overflow: auto;
  min-height: 260px;
  line-height: 1.5;
}

.code-line {
  display: grid;
  grid-template-columns: 2.6rem 1fr;
  gap: 0.6rem;
  padding: 0.15rem 0.4rem;
  border-radius: 0.4rem;
}

.code-line.active {
  background: rgba(255, 209, 102, 0.2);
  color: #fff;
}

.line-no {
  color: rgba(255, 255, 255, 0.5);
  text-align: right;
}

.pane-splitter {
  background: linear-gradient(180deg, transparent, rgba(0, 0, 0, 0.12), transparent);
  cursor: col-resize;
  position: relative;
  touch-action: none;
}

.pane-splitter::after {
  content: "";
  position: absolute;
  top: 40%;
  left: 50%;
  width: 4px;
  height: 40px;
  transform: translateX(-50%);
  border-radius: 4px;
  background: rgba(0, 0, 0, 0.15);
}

.matrix {
  overflow: auto;
  max-height: min(60vh, 520px);
  border: 1px solid var(--border);
  border-radius: 0.8rem;
}

.matrix table {
  border-collapse: collapse;
  width: 100%;
  font-size: 1rem;
}

.matrix th,
.matrix td {
  border: 1px solid var(--border);
  padding: 0.45rem 0.5rem;
  min-width: var(--cell-size);
  text-align: center;
  background: #fff;
}

.matrix thead th {
  position: sticky;
  top: 0;
  z-index: 2;
  background: #f6eee2;
}

.matrix th:first-child {
  position: sticky;
  left: 0;
  z-index: 3;
  background: #f6eee2;
}

.matrix thead th:first-child {
  z-index: 4;
}

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

.cell-current {
  background: rgba(198, 90, 46, 0.2);
  animation: pulse 0.3s ease-in-out;
}

.cell-dep {
  background: rgba(47, 111, 106, 0.2);
}

.cell-write {
  animation: flash 0.35s ease-in-out;
}

.cell-path {
  outline: 2px solid var(--accent-2);
  outline-offset: -2px;
}

.matrix-legend {
  display: flex;
  gap: 0.6rem;
  font-size: 0.75rem;
}

.legend-item {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

.legend-item::before {
  content: "";
  width: 10px;
  height: 10px;
  border-radius: 2px;
  background: var(--border);
  display: inline-block;
}

.legend-item.current::before {
  background: rgba(198, 90, 46, 0.5);
}

.legend-item.dep::before {
  background: rgba(47, 111, 106, 0.5);
}

.legend-item.path::before {
  background: var(--accent-2);
}

.matrix-costs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.85rem;
  margin-bottom: 0.6rem;
}

.cost-pill {
  padding: 0.3rem 0.6rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.8);
}

.cost-pill.active {
  border-color: var(--accent-2);
  color: var(--accent-2);
  font-weight: 600;
}

.matrix-note {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 0.6rem;
}

.watch {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.6rem 1rem;
  font-size: 0.95rem;
}

.watch .choice {
  font-weight: 600;
  color: var(--accent-2);
}

.explanation {
  margin-top: 1rem;
  background: rgba(198, 90, 46, 0.1);
  border: 1px solid rgba(198, 90, 46, 0.2);
  padding: 0.8rem;
  border-radius: 0.8rem;
  min-height: 4.5rem;
}

.edit-panel {
  margin-top: 1rem;
  display: grid;
  gap: 0.6rem;
}

.edit-output {
  font-size: 0.85rem;
  background: rgba(47, 111, 106, 0.08);
  border: 1px solid rgba(47, 111, 106, 0.2);
  border-radius: 0.6rem;
  padding: 0.6rem;
  min-height: 3rem;
}

.sim-status {
  margin-top: 1.2rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  align-items: center;
  justify-content: space-between;
}

.progress {
  font-size: 0.9rem;
  color: var(--muted);
}

.sim-note {
  font-size: 0.85rem;
  color: var(--muted);
  margin: 0;
}

.divider {
  margin: 0 0.4rem;
}

.note {
  background: rgba(47, 111, 106, 0.08);
  border-left: 4px solid var(--accent-2);
  padding: 0.8rem 1rem;
  border-radius: 0.4rem;
}

.c99-block {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 1rem;
  padding: 1rem;
}

.simulator[data-focus="code"] .matrix-pane,
.simulator[data-focus="code"] .watch-pane,
.simulator[data-focus="code"] .pane-splitter {
  display: none;
}

.simulator[data-focus="matrix"] .code-pane,
.simulator[data-focus="matrix"] .watch-pane,
.simulator[data-focus="matrix"] .pane-splitter {
  display: none;
}

.simulator[data-focus="watch"] .code-pane,
.simulator[data-focus="watch"] .matrix-pane,
.simulator[data-focus="watch"] .pane-splitter {
  display: none;
}

.simulator[data-focus="code"] .sim-panes,
.simulator[data-focus="matrix"] .sim-panes,
.simulator[data-focus="watch"] .sim-panes {
  grid-template-columns: 1fr;
}

.simulator.compact .matrix th,
.simulator.compact .matrix td {
  min-width: 2rem;
  padding: 0.3rem;
  font-size: 0.85rem;
}

@keyframes pulse {
  from {
    transform: scale(0.98);
  }
  to {
    transform: scale(1);
  }
}

@keyframes flash {
  0% {
    background: rgba(255, 209, 102, 0.8);
  }
  100% {
    background: transparent;
  }
}

@keyframes depPulse {
  0%,
  60%,
  100% {
    opacity: 0.3;
  }
  20%,
  40% {
    opacity: 0.8;
  }
}

@keyframes currentPulse {
  0%,
  100% {
    opacity: 0.6;
  }
  50% {
    opacity: 1;
  }
}

@keyframes cursorMove {
  0%,
  100% {
    transform: translate(0, 0);
  }
  50% {
    transform: translate(60px, -40px);
  }
}

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

  .pane-splitter {
    display: none;
  }

  .watch-pane {
    grid-column: 1 / -1;
  }
}

@media (max-width: 860px) {
  .sim-panes {
    grid-template-columns: 1fr;
  }

  .watch-pane {
    grid-column: auto;
  }
}

@media (max-width: 720px) {
  .hero {
    padding: 2.5rem 1.2rem 2rem;
  }

  .toc ol {
    columns: 1;
  }

  .simulator {
    padding: 1.4rem;
  }
}

@media (min-width: 900px) {
  .input-row {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .control-row {
    grid-template-columns: repeat(5, auto);
    align-items: center;
  }
}