/* Nought Orbit
   Six color tokens, all defined on :root. Hue 133 throughout.
   bg #0D1C10 · surface #132517 · ink #E2F3E6 · muted #A8C7AF · accent #62DA7C · line #45734F */

:root {
  --bg: #0D1C10;
  --surface: #132517;
  --ink: #E2F3E6;
  --muted: #A8C7AF;
  --accent: #62DA7C;
  --line: #45734F;
  color-scheme: dark;
}

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

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  background-color: var(--bg);
  color: var(--ink);
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  font-size: clamp(0.95rem, 0.9rem + 0.25vw, 1.05rem);
  line-height: 1.65;
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

img,
svg,
canvas {
  max-width: 100%;
}

/* Type */

h1,
h2,
h3 {
  color: var(--ink);
  font-family: inherit;
  font-weight: 700;
  text-wrap: balance;
}

h1 {
  font-size: clamp(1.9rem, 1.2rem + 2.8vw, 3.5rem);
  line-height: 1.08;
  letter-spacing: -0.035em;
  margin: 0 0 1.1rem;
}

h2 {
  font-size: clamp(1.3rem, 1.02rem + 1.2vw, 2.05rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
  margin: 0 0 1.25rem;
}

h3 {
  font-size: clamp(1.02rem, 0.95rem + 0.4vw, 1.25rem);
  line-height: 1.3;
  margin: 0 0 0.4rem;
}

p {
  margin: 0 0 1rem;
  max-width: 66ch;
}

.lede {
  font-size: clamp(1.05rem, 0.98rem + 0.5vw, 1.3rem);
  line-height: 1.5;
}

.eyebrow {
  color: var(--accent);
  font-size: clamp(0.72rem, 0.68rem + 0.2vw, 0.82rem);
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin: 0 0 1rem;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
}

a:hover {
  text-decoration-thickness: 2px;
}

/* Focus and skip link */

:focus:not(:focus-visible) {
  outline: none;
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
canvas:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}

main:focus {
  outline: none;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -4rem;
  z-index: 10;
  padding: 0.6rem 1rem;
  background: var(--accent);
  color: var(--bg);
  font-weight: 700;
  text-decoration: none;
}

.skip-link:focus {
  top: 1rem;
}

/* Layout */

.wrap {
  width: 100%;
  max-width: 72rem;
  margin-inline: auto;
  padding-inline: 1rem;
}

@media (min-width: 40rem) {
  .wrap {
    padding-inline: 2rem;
  }
}

.band {
  border-top: 1px solid var(--line);
  padding-block: clamp(2.5rem, 1.8rem + 3vw, 4.5rem);
}

.page-head {
  border-bottom: 1px solid var(--line);
  padding-block: clamp(2.75rem, 1.8rem + 5vw, 5.5rem) clamp(2rem, 1.4rem + 2.5vw, 3.25rem);
}

.page-head .lede {
  max-width: 48ch;
}

.prose-narrow {
  max-width: 52rem;
}

/* Header and navigation */

.site-header {
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem 1.5rem;
  padding-block: 1rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  color: var(--ink);
  font-weight: 700;
  letter-spacing: 0.02em;
  text-decoration: none;
}

.brand svg {
  width: 2rem;
  height: 2rem;
  flex: none;
}

.mark-ring {
  fill: none;
  stroke: var(--accent);
  stroke-width: 1.5;
}

.mark-dot {
  fill: var(--accent);
}

.site-nav ul {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem 1.25rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-nav a {
  display: inline-block;
  padding-block: 0.2rem;
  color: var(--ink);
  text-decoration: none;
  border-bottom: 2px solid transparent;
}

.site-nav a:hover {
  border-bottom-color: var(--accent);
}

.site-nav a[aria-current="page"] {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

/* Buttons */

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.5rem 0 0;
}

.button {
  display: inline-block;
  padding: 0.8rem 1.1rem;
  border: 2px solid var(--accent);
  background: var(--accent);
  color: var(--bg);
  font: inherit;
  font-weight: 700;
  line-height: 1.2;
  text-decoration: none;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease, border-color 0.2s ease;
}

.button:hover {
  background: var(--ink);
  border-color: var(--ink);
  color: var(--bg);
}

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

.button-ghost:hover {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--bg);
}

.tool-btn {
  padding: 0.6rem 1rem;
  border: 2px solid var(--accent);
  background: transparent;
  color: var(--accent);
  font: inherit;
  font-weight: 700;
  line-height: 1.2;
  cursor: pointer;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.tool-btn:not(:disabled):hover,
.tool-btn[aria-pressed="true"] {
  background: var(--accent);
  color: var(--bg);
}

.tool-btn:disabled {
  border-color: var(--line);
  color: var(--muted);
  cursor: not-allowed;
}

/* Hero and orbit */

.hero {
  padding-block: clamp(2.5rem, 1.5rem + 4vw, 5rem);
}

.hero-grid {
  display: grid;
  gap: 3rem;
  align-items: center;
}

@media (min-width: 56rem) {
  .hero-grid {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
    gap: 4rem;
  }
}

.orbit-wrap {
  width: 100%;
}

.orbit {
  position: relative;
  width: min(100%, 27rem);
  aspect-ratio: 1 / 1;
  margin-inline: auto;
}

.orbit::before {
  content: "";
  position: absolute;
  inset: 16%;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.orbit::after {
  content: "";
  position: absolute;
  inset: 3%;
  border: 1px dashed var(--line);
  border-radius: 50%;
}

.orbit-core {
  position: absolute;
  inset: 35%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.15rem;
  border: 2px solid var(--accent);
  border-radius: 50%;
  background: var(--surface);
  text-align: center;
}

.core-mark {
  color: var(--ink);
  font-size: clamp(1.4rem, 1rem + 2vw, 2.4rem);
  font-weight: 700;
  line-height: 1;
  letter-spacing: -0.05em;
}

.core-caption {
  color: var(--muted);
  font-size: clamp(0.6rem, 0.55rem + 0.2vw, 0.72rem);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

/* Four orbit slots at 0, 90, 180 and 270 degrees. The ring turns slowly; each
   label counter-turns by the same amount so it stays upright. */
.orbit-ring {
  position: absolute;
  inset: 16%;
  margin: 0;
  padding: 0;
  list-style: none;
  animation: orbit-spin 90s linear infinite;
}

.orbit-ring li {
  position: absolute;
  inset: 0;
  transform: rotate(var(--a));
}

.orbit-ring li:nth-child(1) { --a: 0deg; }
.orbit-ring li:nth-child(2) { --a: 90deg; }
.orbit-ring li:nth-child(3) { --a: 180deg; }
.orbit-ring li:nth-child(4) { --a: 270deg; }

.orbit-ring a {
  position: absolute;
  left: 50%;
  top: 0;
  display: inline-block;
  padding: 0.55em 0.95em;
  border: 2px solid var(--accent);
  border-radius: 999px;
  background: var(--bg);
  color: var(--ink);
  font-size: clamp(0.78rem, 0.72rem + 0.3vw, 0.92rem);
  font-weight: 700;
  letter-spacing: 0.1em;
  line-height: 1.2;
  text-decoration: none;
  text-transform: uppercase;
  white-space: nowrap;
  transform: translate(-50%, -50%) rotate(calc(var(--a) * -1));
  animation: orbit-upright 90s linear infinite;
  transition: background-color 0.2s ease, color 0.2s ease;
}

.orbit-ring a:hover,
.orbit-ring a:focus-visible {
  background: var(--accent);
  color: var(--bg);
}

.orbit-ring.is-paused,
.orbit-ring.is-paused a,
.orbit:focus-within .orbit-ring,
.orbit:focus-within .orbit-ring a {
  animation-play-state: paused;
}

.orbit-caption {
  max-width: 40ch;
  margin: 1.25rem auto 0;
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}

.orbit-tools {
  align-items: center;
  gap: 0.6rem;
  margin-top: 1rem;
  text-align: center;
}

@keyframes orbit-spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

@keyframes orbit-upright {
  from { transform: translate(-50%, -50%) rotate(calc(var(--a) * -1)); }
  to { transform: translate(-50%, -50%) rotate(calc(var(--a) * -1 - 360deg)); }
}

/* Lists used as rows */

.rows,
.link-rows,
.plain-list,
.key-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.rows {
  border-top: 1px solid var(--line);
}

.rows li {
  display: grid;
  grid-template-columns: 3rem minmax(0, 1fr);
  gap: 1rem;
  padding-block: 1.5rem;
  border-bottom: 1px solid var(--line);
}

.rows p {
  margin: 0;
  color: var(--muted);
}

.num {
  color: var(--accent);
  font-size: clamp(1rem, 0.95rem + 0.4vw, 1.25rem);
  font-weight: 700;
}

.link-rows {
  border-top: 1px solid var(--line);
}

.link-rows li {
  border-bottom: 1px solid var(--line);
}

.static-row {
  display: grid;
  gap: 0.35rem;
  padding-block: 1.5rem;
}

.link-rows a {
  display: grid;
  gap: 0.35rem;
  padding-block: 1.5rem;
  color: var(--ink);
  text-decoration: none;
}

.row-label {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.row-title {
  font-size: clamp(1.1rem, 1rem + 0.8vw, 1.5rem);
  font-weight: 700;
  text-decoration: underline;
  text-decoration-color: var(--line);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.25em;
}

.row-text {
  max-width: 60ch;
  color: var(--muted);
}

.link-rows a:hover .row-title,
.link-rows a:focus-visible .row-title {
  color: var(--accent);
  text-decoration-color: var(--accent);
}

.plain-list li {
  position: relative;
  padding-left: 1.5rem;
  margin-bottom: 0.9rem;
  max-width: 66ch;
}

.plain-list li::before {
  content: "";
  position: absolute;
  left: 0.15rem;
  top: 0.6em;
  width: 0.55rem;
  height: 0.55rem;
  border: 2px solid var(--accent);
  border-radius: 50%;
}

/* Notes, glossary and prose */

.note {
  max-width: 60ch;
  padding: 1rem 1.25rem;
  border: 2px solid var(--accent);
  background: var(--surface);
}

.note p:last-child {
  margin-bottom: 0;
}

.glossary {
  display: grid;
  gap: 1.1rem;
  margin: 0;
}

.glossary div {
  padding-left: 1rem;
  border-left: 2px solid var(--accent);
}

.glossary dt {
  color: var(--ink);
  font-weight: 700;
}

.glossary dd {
  margin: 0.25rem 0 0;
  color: var(--muted);
  max-width: 60ch;
}

.question-no {
  color: var(--accent);
}

.worked {
  padding: 1.25rem 1.4rem;
  border-left: 2px solid var(--line);
}

.diagram {
  display: block;
  width: min(100%, 36rem);
  height: auto;
  margin: 1.5rem 0 0;
}

.diagram .ring {
  fill: var(--surface);
  stroke: var(--accent);
  stroke-width: 2;
}

.diagram .arrow {
  fill: none;
  stroke: var(--accent);
  stroke-width: 2;
}

.diagram .big {
  fill: var(--ink);
  font-size: 64px;
  font-weight: 700;
}

.diagram .cap {
  fill: var(--muted);
  font-size: 15px;
}

.diagram text {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

.mail-link {
  display: inline-block;
  font-size: clamp(1.2rem, 1rem + 1.4vw, 2.1rem);
  font-weight: 700;
  overflow-wrap: anywhere;
}

.two-col {
  display: grid;
  gap: 2.5rem;
}

@media (min-width: 48rem) {
  .two-col {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 3.5rem;
  }
}

/* Sketch pad */

.no-js-note {
  display: block;
  max-width: 60ch;
  padding: 1rem 1.25rem;
  border: 2px dashed var(--line);
  color: var(--muted);
}

.js-only {
  display: none;
}

.js .js-only {
  display: block;
}

.js .no-js-note {
  display: none;
}

.js .pad-tool {
  display: grid;
  gap: 1.25rem;
}

.js .orbit-tools {
  display: flex;
}

.pad-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: 1rem 1.25rem;
}

.field {
  display: grid;
  gap: 0.35rem;
  flex: 1 1 14rem;
  min-width: 0;
}

.field label {
  font-weight: 700;
}

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

.field input[type="range"] {
  width: 100%;
  margin: 0.4rem 0;
  accent-color: var(--accent);
}

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

.pad-frame {
  position: relative;
  border: 2px solid var(--accent);
  background: var(--surface);
}

.pad-canvas {
  display: block;
  width: 100%;
  height: auto;
  touch-action: none;
  user-select: none;
  -webkit-user-select: none;
  cursor: crosshair;
}

.pad-overlay {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

.status {
  min-height: 1.6em;
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.key-list li {
  margin-bottom: 0.6rem;
  max-width: 66ch;
}

.key-list kbd {
  padding: 0.05em 0.4em;
  border: 1px solid var(--accent);
  color: var(--ink);
  font: inherit;
  font-size: 0.9em;
}

/* Footer */

.site-footer {
  margin-top: auto;
  padding-block: 2.25rem;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.9rem;
}

.footer-inner {
  display: grid;
  gap: 0.4rem;
}

.footer-inner p {
  margin: 0;
}

.footer-brand {
  color: var(--ink);
  font-weight: 700;
}

.site-footer a {
  color: var(--accent);
}

/* Motion: every transition and animation has a static form */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .orbit-ring,
  .orbit-ring a {
    animation: none;
  }

  .button,
  .tool-btn,
  .orbit-ring a,
  .site-nav a {
    transition: none;
  }
}