/* A document: one column of text, figures a little wider, notes at the end.
   Copy marked <mark class="todo"> is still to be written or measured. */
:root {
  --paper: #FFFFFF; --ink: #1B1A17; --body: #2F2D29; --muted: #6F6B63;
  --faint: #A9A49A; --rule: #E7E3DA; --tint: #F6F4EF;
  --serif: Charter, "Iowan Old Style", "Source Serif 4", Cambria, Georgia, "Songti SC", "Noto Serif SC", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI Variable Text", "Segoe UI", system-ui, "PingFang SC", "Microsoft YaHei", sans-serif;
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;
  --text: 640px;
  --wide: 880px;
  color-scheme: light;
}
* { box-sizing: border-box; }
html { background: var(--paper); color: var(--body); -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility; scroll-padding-top: 24px; }
body { margin: 0; font: 18px/1.7 var(--serif); }
a { color: inherit; text-decoration: underline; text-decoration-color: var(--faint); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { text-decoration-color: var(--ink); }

/* An endless tilted grid behind everything, slowly zooming in (drawn by the
   script at the end). It fades toward the text column so it never sits
   under the reading. */
.grid { position: fixed; inset: 0; z-index: -1; width: 100%; height: 100%; pointer-events: none;
  --fade: linear-gradient(to right, #000, rgba(0, 0, 0, .3) calc(50% - 380px), rgba(0, 0, 0, .12) 50%, rgba(0, 0, 0, .3) calc(50% + 380px), #000);
  -webkit-mask-image: var(--fade); mask-image: var(--fade); }

.top { display: flex; align-items: center; gap: 24px; max-width: var(--wide); margin: 0 auto; padding: 22px 24px; font: 14px var(--sans); }
.top a { text-decoration: none; color: var(--muted); }
.top a:hover { color: var(--ink); }
.top .brand { display: flex; align-items: center; gap: 9px; margin-right: auto; color: var(--ink); font-weight: 600; }
.top .brand img { width: 20px; height: 20px; border-radius: 5px; }
.top a[aria-current="page"] { color: var(--ink); }
/* English and Chinese: each page links to itself in the other language. */
.top .lang { padding-left: 16px; border-left: 1px solid var(--rule); }

/* Text in the middle column; the contents in the left margin, clear of the
   wider figures, when there is room. */
.page { display: grid; grid-template-columns: 1fr min(var(--text), 100% - 48px) 1fr; padding: 48px 0 96px; }
.page > * { grid-column: 2; }
.toc { grid-column: 1; grid-row: 1 / span 99; justify-self: end; position: sticky; top: 32px; align-self: start; width: 180px; margin-right: calc((var(--wide) - var(--text)) / 2 + 32px); padding-top: 6px; font: 13.5px/1.5 var(--sans); }
.toc .label { margin-bottom: 10px; font-size: 12px; color: var(--faint); }
.toc ol { margin: 0; padding: 0; list-style: none; counter-reset: s; }
.toc li { display: flex; margin: 0 0 7px; counter-increment: s; }
.toc li::before { content: counter(s); flex: none; width: 26px; color: var(--faint); font-variant-numeric: tabular-nums; }
.toc a { display: inline-flex; align-items: center; gap: 7px; color: var(--muted); text-decoration: none; }
.toc svg.ic { width: 15px; height: 15px; color: var(--faint); }
.toc a:hover svg.ic { color: var(--ink); }
.toc a:hover { color: var(--ink); }
@media (max-width: 1340px) { .toc { display: none; } }

h1 { margin: 0; font: 600 44px/1.15 var(--serif); letter-spacing: -.015em; color: var(--ink); }
.subtitle { margin: 10px 0 0; font-size: 23px; line-height: 1.4; color: var(--muted); }
.meta { margin: 22px 0 0; font: 13.5px/1.6 var(--sans); color: var(--muted); }
.meta span + span::before { content: "·"; margin: 0 8px; color: var(--faint); }

.actions { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin: 30px 0 0; font: 15px var(--sans); }
.button { display: inline-flex; align-items: center; height: 40px; padding: 0 16px; font: 500 15px var(--sans); white-space: nowrap; border: 1px solid var(--rule); border-radius: 6px; color: var(--ink); font-weight: 500; text-decoration: none; }
.button:hover { border-color: var(--faint); }
.button.primary { background: var(--ink); border-color: var(--ink); color: var(--paper); }
.button.primary:hover { background: #000; }
.actions .note { margin-left: 6px; font-size: 13.5px; color: var(--muted); }

h2 { margin: 72px 0 18px; font: 600 27px/1.3 var(--serif); letter-spacing: -.01em; color: var(--ink); counter-increment: h2; }
svg.ic { width: 1em; height: 1em; flex: none; fill: none; stroke: currentColor; stroke-width: 1.75; stroke-linecap: round; stroke-linejoin: round; }
svg.ic.logo { stroke: none; }
h2 svg.ic { margin-right: .4em; color: var(--muted); vertical-align: -.12em; stroke-width: 1.6; }
.button svg.ic { width: 18px; height: 18px; margin-right: 8px; }
.top svg.ic { width: 17px; height: 17px; margin-right: 6px; vertical-align: -3px; }
ul.features { padding-left: 0; list-style: none; }
ul.features li { display: grid; grid-template-columns: 30px 1fr; }
ul.features li > svg.ic { width: 19px; height: 19px; margin-top: .3em; color: var(--muted); }
h2::before { content: counter(h2); display: inline-block; min-width: 1.4em; color: var(--faint); font-weight: 400; }
.page { counter-reset: h2 fig tab; }
p { margin: 0 0 1.1em; }
ul, ol { margin: 0 0 1.1em; padding-left: 1.3em; }
li { margin: 0 0 .45em; }
li::marker { color: var(--faint); }
strong { color: var(--ink); font-weight: 600; }
code { padding: .1em .35em; border-radius: 4px; background: var(--tint); font: .82em var(--mono); }
kbd { padding: .05em .4em; border: 1px solid var(--rule); border-bottom-width: 2px; border-radius: 4px; font: .78em var(--sans); }
mark.todo { padding: 0 .2em; border-radius: 3px; background: #FFF1B8; color: #6B5300; }

/* Figures run wider than the text; their captions keep to the text's measure. */
figure { margin: 40px calc(50% - min(var(--wide), 100vw - 48px) / 2); counter-increment: fig; }
figure .img { position: relative; overflow: hidden; border: 1px solid var(--rule); border-radius: 10px; background: var(--tint); box-shadow: 0 1px 2px rgba(0, 0, 0, .04), 0 16px 40px -20px rgba(0, 0, 0, .22); }
figure img { display: block; width: 100%; height: auto; }
figure .img.missing { aspect-ratio: 16 / 10; }
figure .img + .img { margin-top: 24px; }
figure .img.missing img { visibility: hidden; }
figure .img.missing::after { content: attr(data-src); position: absolute; inset: 0; display: grid; place-items: center; font: 13px var(--mono); color: var(--faint); }
figcaption { max-width: var(--text); margin: 14px auto 0; font: 14px/1.55 var(--sans); color: var(--muted); }
figcaption::before { content: "Figure " counter(fig) ". "; color: var(--ink); font-weight: 600; }
:lang(zh) figcaption::before { content: "图 " counter(fig) "　"; }

.table { margin: 28px 0 32px; counter-increment: tab; }
table { width: 100%; border-collapse: collapse; font: 15px/1.5 var(--sans); font-variant-numeric: tabular-nums; }
th, td { padding: 9px 12px 9px 0; border-bottom: 1px solid var(--rule); text-align: right; }
th:first-child, td:first-child { text-align: left; }
thead th { border-bottom-color: var(--ink); font-weight: 600; color: var(--ink); }
tbody td:nth-child(2) { color: var(--ink); font-weight: 600; }
td { color: var(--muted); }
.table .caption { margin-top: 12px; font: 14px/1.55 var(--sans); color: var(--muted); }
.table .caption::before { content: "Table " counter(tab) ". "; color: var(--ink); font-weight: 600; }
:lang(zh) .table .caption::before { content: "表 " counter(tab) "　"; }

sup { line-height: 0; font: 12px var(--sans); }
sup a { text-decoration: none; color: var(--muted); }
.notes { margin-top: 72px; padding-top: 20px; border-top: 1px solid var(--rule); font: 14px/1.6 var(--sans); color: var(--muted); }
.notes ol { padding-left: 1.2em; }
.notes :target { background: var(--tint); }

.play { display: inline-flex; align-items: center; gap: 6px; height: 28px; padding: 0 11px 0 9px; border: 1px solid var(--rule); border-radius: 6px; background: var(--paper); color: var(--ink); font: 500 14px var(--sans); vertical-align: 1px; cursor: pointer; }
.play:hover { border-color: var(--faint); }
.play svg.ic { width: 15px; height: 15px; }
.play .stop { display: none; }
.play.playing .start { display: none; }
.play.playing .stop { display: block; }

footer { margin-top: 40px; font: 13px/1.6 var(--sans); color: var(--faint); }

@media (max-width: 640px) {
  body { font-size: 17px; }
  h1 { font-size: 36px; }
  .subtitle { font-size: 20px; }
  h2 { margin-top: 56px; font-size: 24px; }
  th, td { padding-right: 8px; font-size: 14px; }
}
@media print {
  .grid, .top, .toc, .actions { display: none; }
  .page { padding-top: 0; }
}

/* The icon sprite each page carries. */
.sprite { position: absolute; width: 0; height: 0; }

/* The download page. */
h2.plain { counter-increment: none; }
h2.plain::before { content: none; }
.platforms { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 40px 0 8px; }
/* A column, its text taking the slack: the buttons of both line up at the bottom. */
.platform { display: flex; flex-direction: column; padding: 22px 24px 24px; border: 1px solid var(--rule); border-radius: 10px; background: var(--paper); }
.platform h2 { display: flex; align-items: center; gap: 10px; margin: 0 0 8px; font-size: 24px; }
.platform h2 svg.ic { margin: 0; width: 22px; height: 22px; color: var(--ink); }
.platform p { flex: 1; margin: 0 0 20px; font: 15px/1.55 var(--sans); color: var(--muted); }
.platform .get { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; }
.platform .size { margin-left: 4px; font: 13.5px var(--sans); color: var(--muted); white-space: nowrap; }
@media (max-width: 640px) { .platforms { grid-template-columns: 1fr; } }

/* The changelog (made by tool/build_changelog.dart): a version a section,
   its heading a link to itself; the version the app links to is marked. */
.release { margin-top: 56px; padding-top: 4px; }
.release h2 { margin: 0 0 14px; font-size: 26px; }
.release h2 a { text-decoration: none; }
.release h2 a:hover { text-decoration: underline; text-decoration-color: var(--faint); }
.release :is(p, li) { font-size: 17px; }
.release p:has(+ ul) { margin: 20px 0 6px; font: 600 13.5px/1.5 var(--sans); color: var(--muted); }
.release h2 + p:has(+ ul) { margin-top: 0; }
.release:target h2 a { box-shadow: inset 0 -.35em 0 var(--tint); }

/* The download page's thanks, with its ask for a star (download.js). */
dialog.star { max-width: min(460px, calc(100vw - 48px)); padding: 26px 28px 24px; border: 1px solid var(--rule); border-radius: 12px; background: var(--paper); color: var(--body); box-shadow: 0 24px 64px -24px rgba(0, 0, 0, .35); }
dialog.star::backdrop { background: rgba(27, 26, 23, .28); }
dialog.star h2 { margin: 0 0 10px; font-size: 22px; }
dialog.star p { margin: 0 0 22px; font: 15px/1.6 var(--sans); color: var(--muted); }
dialog.star .get { display: flex; flex-wrap: wrap; gap: 8px; }
dialog.star button.button { background: var(--paper); cursor: pointer; }