/* Plain Screen — one stylesheet, no dependencies. */

:root {
  --paper: #f1ede4;
  --panel: #fbf8f1;
  --ink: #15130f;
  --ink-soft: #3f3a31;
  --muted: #726a5c;
  --rule: #d3cab8;
  --rule-soft: #e3dccd;
  --accent: #b23a12;
  --accent-ink: #fff9f2;
  --grain: rgba(21, 19, 15, .055);

  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, "Songti SC", "Source Han Serif SC", "Noto Serif CJK SC", Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #121110;
    --panel: #1a1815;
    --ink: #efe9dc;
    --ink-soft: #cfc7b7;
    --muted: #948b7b;
    --rule: #322e27;
    --rule-soft: #262320;
    --accent: #e4703f;
    --accent-ink: #1a0d06;
    --grain: rgba(255, 255, 255, .045);
  }
}

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

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  background-color: var(--paper);
  background-image: radial-gradient(var(--grain) .5px, transparent .6px);
  background-size: 4px 4px;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

:lang(zh) {
  line-height: 1.8;
}

img, svg, canvas { max-width: 100%; }
a { color: inherit; text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--accent); }
p { margin: 0 0 1em; }
p:last-child { margin-bottom: 0; }

::selection { background: var(--ink); color: var(--paper); }

.wrap {
  width: 100%;
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 28px;
}
@media (max-width: 560px) {
  .wrap { padding: 0 20px; }
}

.vh {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px; padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* ---------- header ---------- */

.site-head {
  display: flex;
  align-items: center;
  gap: 24px;
  padding: 20px 0 18px;
  border-bottom: 1px solid var(--rule);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  font-family: var(--serif);
  font-size: 20px;
  letter-spacing: -.01em;
  text-decoration: none;
  color: var(--ink);
  margin-right: auto;
}
.brand .mark {
  width: 15px; height: 15px;
  background: var(--ink);
  outline: 1px solid var(--ink);
  outline-offset: 2px;
  flex: none;
}
.brand:hover .mark { background: var(--accent); outline-color: var(--accent); }

.nav {
  display: flex;
  gap: 26px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .13em;
  text-transform: uppercase;
}
.nav a { text-decoration: none; color: var(--muted); padding: 4px 0; }
.nav a:hover { color: var(--ink); }
.nav a[aria-current="page"] { color: var(--ink); box-shadow: inset 0 -1px 0 var(--ink); }

.lang {
  display: flex;
  align-items: center;
  gap: 7px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
  border-left: 1px solid var(--rule);
  padding-left: 18px;
}
.lang a { text-decoration: none; color: var(--muted); }
.lang a:hover, .lang a[aria-current="true"] { color: var(--ink); }
.lang .sep { color: var(--rule); }

@media (max-width: 720px) {
  .site-head { flex-wrap: wrap; gap: 14px; padding: 16px 0; }
  .nav { order: 3; width: 100%; gap: 20px; overflow-x: auto; }
  .lang { border-left: 0; padding-left: 0; }
}

/* ---------- hero ---------- */

.hero { padding: 68px 0 46px; }

.eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 22px;
  display: flex;
  align-items: center;
  gap: 12px;
}
.eyebrow::after {
  content: "";
  flex: 1;
  max-width: 180px;
  height: 1px;
  background: var(--rule);
}

h1 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.6rem, 6.4vw, 4.7rem);
  line-height: .96;
  letter-spacing: -.028em;
  margin: 0 0 .42em;
  max-width: 17ch;
  text-wrap: balance;
}
:lang(zh) h1 {
  font-size: clamp(2.2rem, 5.6vw, 3.9rem);
  line-height: 1.18;
  letter-spacing: .008em;
  max-width: 20ch;
}
h1 em { font-style: italic; color: var(--accent); }

.lede {
  font-size: 18px;
  line-height: 1.62;
  color: var(--ink-soft);
  max-width: 52ch;
  margin: 0 0 8px;
}
:lang(zh) .lede { font-size: 17px; max-width: 44ch; }

.hero-foot {
  margin-top: 26px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .06em;
  color: var(--muted);
  display: flex;
  flex-wrap: wrap;
  gap: 6px 18px;
}
.hero-foot span { white-space: nowrap; }

/* ---------- tool ---------- */

.panel-sect {
  padding: 56px 0 0;
  border-top: 1px solid var(--rule);
}

.tool {
  display: grid;
  grid-template-columns: minmax(0, 1.5fr) minmax(290px, 1fr);
  gap: 42px;
  align-items: start;
  padding: 32px 0 64px;
}
@media (max-width: 900px) {
  .tool { grid-template-columns: 1fr; gap: 30px; padding-top: 32px; }
}

.stage {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 10;
  background-color: var(--c, #000);
  border: 1px solid var(--ink);
  outline: 1px solid var(--rule);
  outline-offset: 5px;
  --pat-ink: rgba(0, 0, 0, .16);
  --pat-soft: rgba(0, 0, 0, .09);
  --pat-strong: rgba(0, 0, 0, .5);
}
.stage[data-pattern="dots"] {
  background-image: radial-gradient(circle at 50% 50%, var(--pat-ink) 1.1px, transparent 1.6px);
  background-size: 18px 18px;
}
.stage[data-pattern="stripes"] {
  background-image: repeating-linear-gradient(45deg, var(--pat-ink) 0 6px, transparent 6px 19px);
}
.stage[data-pattern="checks"] {
  background-image: conic-gradient(var(--pat-soft) 0 25%, transparent 0 50%, var(--pat-soft) 0 75%, transparent 0);
  background-size: 26px 26px;
}
.stage[data-pattern="fade"] {
  background-image: linear-gradient(155deg, transparent 12%, var(--pat-strong) 100%);
}

.stage:fullscreen {
  aspect-ratio: auto;
  width: 100vw;
  height: 100vh;
  border: 0;
  outline: 0;
}
.stage:fullscreen .stage-hint { opacity: 1; }

.stage-hint {
  position: absolute;
  right: 20px;
  bottom: 16px;
  margin: 0;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .08em;
  color: var(--pat-ink);
  opacity: 0;
  transition: opacity .4s ease .3s;
  pointer-events: none;
}

.stage-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 14px;
  margin: 16px 0 0;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .06em;
  color: var(--muted);
}
.stage-meta b {
  font-weight: 400;
  color: var(--ink);
}

.noscript {
  margin: 18px 0 0;
  padding: 10px 12px;
  border: 1px solid var(--rule);
  background: var(--panel);
  font-size: 13px;
  color: var(--muted);
}

/* controls */

.controls { display: grid; gap: 26px; }

.field { display: grid; gap: 11px; }

.label {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--muted);
}

.swatches, .chips { display: flex; flex-wrap: wrap; gap: 9px; margin: 0; padding: 0; border: 0; }

.swatches input, .chips input {
  position: absolute;
  opacity: 0;
  width: 1px; height: 1px;
}

.swatches label {
  display: block;
  width: 34px; height: 34px;
  background: var(--sw, #000);
  border: 1px solid rgba(128, 128, 128, .5);
  cursor: pointer;
  outline: 1px solid transparent;
  outline-offset: 2px;
  transition: outline-color .12s;
}
.swatches label:hover { outline-color: var(--muted); }
.swatches input:checked + label { outline: 2px solid var(--ink); outline-offset: 2px; }
.swatches input:focus-visible + label { outline: 2px solid var(--accent); outline-offset: 3px; }

.chips label {
  display: inline-block;
  padding: 6px 12px;
  border: 1px solid var(--rule);
  background: var(--panel);
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--ink-soft);
  cursor: pointer;
  user-select: none;
}
.chips label:hover { border-color: var(--muted); }
.chips input:checked + label {
  background: var(--ink);
  border-color: var(--ink);
  color: var(--paper);
}
.chips input:focus-visible + label { outline: 2px solid var(--accent); outline-offset: 2px; }

.hexrow { display: flex; gap: 10px; align-items: stretch; }

input[type="color"] {
  width: 46px;
  height: 42px;
  padding: 0;
  border: 1px solid var(--rule);
  background: var(--panel);
  cursor: pointer;
  flex: none;
}
input[type="color"]::-webkit-color-swatch-wrapper { padding: 4px; }
input[type="color"]::-webkit-color-swatch { border: 1px solid rgba(128, 128, 128, .4); }

input[type="text"], select {
  font-family: var(--mono);
  font-size: 13px;
  letter-spacing: .04em;
  color: var(--ink);
  background: var(--panel);
  border: 1px solid var(--rule);
  border-radius: 0;
  padding: 10px 12px;
  width: 100%;
  height: 42px;
  appearance: none;
  -webkit-appearance: none;
}
input[type="text"]:focus, select:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: var(--accent);
}
input[type="text"]:invalid {
  border-color: var(--accent);
  box-shadow: inset 0 -2px 0 var(--accent);
}

select {
  cursor: pointer;
  padding-right: 34px;
  background-image: linear-gradient(45deg, transparent 50%, var(--muted) 50%), linear-gradient(135deg, var(--muted) 50%, transparent 50%);
  background-position: calc(100% - 18px) 19px, calc(100% - 13px) 19px;
  background-size: 5px 5px, 5px 5px;
  background-repeat: no-repeat;
}

.actions { display: flex; flex-wrap: wrap; gap: 9px; }

.btn {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .1em;
  text-transform: uppercase;
  padding: 0 18px;
  height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 1px solid var(--ink);
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  transition: background .14s, color .14s, border-color .14s;
}
.btn:hover { background: var(--ink); color: var(--paper); }
.btn:active { transform: translateY(1px); }
.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.btn-primary { background: var(--ink); color: var(--paper); flex: 1 1 140px; }
.btn-primary:hover { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }

.btn-quiet { border-color: var(--rule); color: var(--muted); }
.btn-quiet:hover { background: transparent; border-color: var(--ink); color: var(--ink); }

.js-only { display: none; }
html.js .js-only { display: inline-flex; }

/* ---------- sections ---------- */

.sect { padding: 58px 0; border-top: 1px solid var(--rule); }

.sect-head { margin-bottom: 34px; }
.sect-head .num {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: .18em;
  color: var(--accent);
  display: block;
  margin-bottom: 10px;
}
h2 {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.55rem, 3vw, 2.15rem);
  line-height: 1.15;
  letter-spacing: -.015em;
  margin: 0 0 .35em;
  text-wrap: balance;
}
:lang(zh) h2 { letter-spacing: 0; line-height: 1.35; }
.sect-head p { color: var(--muted); max-width: 58ch; margin: 0; font-size: 16px; }

/* uses */

.uses {
  margin: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  column-gap: 48px;
}
@media (max-width: 760px) { .uses { grid-template-columns: 1fr; } }

.use {
  display: grid;
  gap: 5px;
  padding: 18px 0 20px;
  border-top: 1px solid var(--rule-soft);
}
.use dt {
  font-family: var(--serif);
  font-size: 19px;
  letter-spacing: -.01em;
  color: var(--ink);
}
.use dd {
  margin: 0;
  font-size: 15px;
  line-height: 1.6;
  color: var(--muted);
  max-width: 40ch;
}

/* colour index */

.colour-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(148px, 1fr));
  gap: 1px;
  background: var(--rule-soft);
  border: 1px solid var(--rule-soft);
}
.colour-grid a {
  display: grid;
  gap: 10px;
  padding: 14px;
  background: var(--paper);
  text-decoration: none;
  transition: background .14s;
}
.colour-grid a:hover { background: var(--panel); color: var(--ink); }
.colour-grid .chip {
  display: block;
  height: 62px;
  background: var(--sw);
  border: 1px solid rgba(128, 128, 128, .35);
}
.colour-grid .nm {
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.2;
}
.colour-grid .hx {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .06em;
  color: var(--muted);
}
.colour-grid a:hover .hx { color: var(--accent); }

/* steps */

.steps { list-style: none; margin: 0; padding: 0; counter-reset: s; display: grid; gap: 0; }
.steps li {
  counter-increment: s;
  display: grid;
  grid-template-columns: 54px minmax(0, 1fr);
  gap: 20px;
  padding: 22px 0;
  border-top: 1px solid var(--rule-soft);
}
.steps li::before {
  content: counter(s, decimal-leading-zero);
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: .1em;
  color: var(--accent);
  padding-top: 5px;
}
.steps h3 {
  grid-column: 2;
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 400;
  margin: 0 0 3px;
}
.steps p { grid-column: 2; margin: 0; color: var(--muted); font-size: 15px; max-width: 56ch; }
.steps kbd, .key {
  font-family: var(--mono);
  font-size: 11.5px;
  border: 1px solid var(--rule);
  background: var(--panel);
  padding: 1px 5px;
  color: var(--ink);
  white-space: nowrap;
}

/* limits */

.limits { list-style: none; margin: 0; padding: 0; display: grid; gap: 0; }
.limits li {
  display: grid;
  grid-template-columns: 22px minmax(0, 1fr);
  gap: 14px;
  padding: 18px 0;
  border-top: 1px solid var(--rule-soft);
  font-size: 15.5px;
  color: var(--ink-soft);
}
.limits li::before {
  content: "—";
  color: var(--accent);
  font-family: var(--mono);
  font-size: 12px;
  line-height: 1.9;
}
.limits strong { font-weight: 600; color: var(--ink); }

/* faq */

.faq { border-top: 1px solid var(--rule-soft); }
.faq details { border-bottom: 1px solid var(--rule-soft); }
.faq summary {
  cursor: pointer;
  padding: 17px 34px 17px 0;
  position: relative;
  font-size: 16.5px;
  list-style: none;
  color: var(--ink);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after {
  content: "+";
  position: absolute;
  right: 2px;
  top: 15px;
  font-family: var(--mono);
  font-size: 15px;
  color: var(--muted);
}
.faq details[open] summary::after { content: "−"; color: var(--accent); }
.faq summary:hover { color: var(--accent); }
.faq summary:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.faq .ans {
  padding: 0 34px 20px 0;
  margin: 0;
  color: var(--muted);
  font-size: 15.5px;
  max-width: 66ch;
}
.faq .ans code, code {
  font-family: var(--mono);
  font-size: .88em;
  background: var(--panel);
  border: 1px solid var(--rule-soft);
  padding: 1px 5px;
  white-space: nowrap;
}

/* colour page */

.colour-hero { padding: 56px 0 40px; }
.colour-hero .swatch-big {
  width: 100%;
  height: 8px;
  background: var(--c);
  border: 1px solid var(--ink);
  margin-bottom: 30px;
}
.colour-hero h1 { max-width: 14ch; }

.pager {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 22px;
  margin-top: 34px;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: .06em;
}
.pager a { color: var(--muted); text-decoration: none; padding: 3px 0; }
.pager a:hover { color: var(--ink); }
.pager .cur { color: var(--ink); border-bottom: 1px solid var(--ink); }

/* footer */

.site-foot {
  border-top: 1px solid var(--rule);
  padding: 34px 0 46px;
  display: flex;
  flex-wrap: wrap;
  gap: 18px 40px;
  justify-content: space-between;
  font-size: 13.5px;
  color: var(--muted);
}
.site-foot p { margin: 0; max-width: 46ch; }
.site-foot nav { display: flex; gap: 10px 20px; flex-wrap: wrap; font-family: var(--mono); font-size: 11px; letter-spacing: .08em; text-transform: uppercase; }
.site-foot a { text-decoration: none; color: var(--muted); }
.site-foot a:hover { color: var(--ink); }

/* dialog */

dialog {
  border: 1px solid var(--ink);
  background: var(--panel);
  color: var(--ink);
  padding: 26px;
  max-width: 460px;
  width: calc(100% - 40px);
}
dialog::backdrop { background: rgba(10, 9, 7, .45); }
dialog h2 { font-size: 1.35rem; margin-bottom: .4em; }
dialog p { color: var(--muted); font-size: 14.5px; }
dialog .hexrow { margin: 16px 0; }
dialog .actions { margin-top: 18px; }
dialog .actions .btn { flex: 0 1 auto; }