/* ==========================================================================
   Homepage style sheet (Chinese and English)

   All visual decisions live in the token table below. Components only use
   var(--token). To change the look, edit :root. To add or switch a reading
   style, add another [data-style="..."] block that overrides tokens; the
   layout rules stay untouched.
   ========================================================================== */

:root {
  /* Type */
  --font-serif: Georgia, 'Songti SC', 'Noto Serif SC', 'Noto Serif CJK SC', 'Source Han Serif SC', 'Source Han Serif CN', 'STSong', 'SimSun', serif;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Noto Sans CJK SC', 'Microsoft YaHei', sans-serif;
  --font-mono: Consolas, 'Courier New', Monaco, monospace;
  --font-body: var(--font-serif);
  --base-size: 17px;
  --leading: 1.92;
  --tracking: .012em;
  --measure: 780px;

  /* Paper and ink */
  --paper: #F7F4EC;
  --paper-deep: #F1EDE3;
  --paper-card: #FCFAF4;
  --paper-note: #F3EFE4;
  --ink: #3B3731;
  --ink-strong: #2E2B26;
  --ink-soft: #6F695F;
  --ink-faint: #8C8579;
  --rule: #E2DCCF;
  --rule-strong: #B7AE9D;
  --celadon: #93A395;
  --celadon-deep: #5E6F63;
  --ochre: #A98A5F;

  /* Links and accents */
  --link: var(--celadon-deep);
  --link-hover: #8A6C45;
  --link-line: rgba(94, 111, 99, .28);
  --link-line-hover: rgba(138, 108, 69, .45);
  --selection: #DDE4D8;
  --h1-rule: #C4B79E;

  /* Notes and code */
  --note-bg: var(--paper-note);
  --note-border: #E2DBCD;
  --note-ink: #57524A;
  --code-bg: #EAF5FA;
  --code-border: #D5E8EE;
  --code-ink: #263638;
  --code-kw: #4F6B5B;
  --code-ty: #7A5533;
  --code-fn: #3F5E68;
  --code-st: #8A5543;
  --code-cm: #6F7A74;
  --code-nm: #6A573C;
  --code-pr: #6E5C43;
  --inline-code-ink: #6B5D49;
  --inline-code-bg: #F0EBE0;

  /* Controls and chrome */
  --btn-border: var(--rule-strong);
  --btn-border-hover: #8C8578;
  --btn-bg-hover: #EFEAE0;
  --tag-rule: #D7D0C2;
  --pref-active-bg: #EFEAE0;

  /* Sizes and spacing */
  --h1-size: clamp(1.55rem, 3.6vw, 1.95rem);
  --h2-size: 1.06rem;
  --h3-size: .91rem;
  --note-size: .91rem;
  --small-size: .76rem;
  --meta-size: .735rem;
  --btn-size: .82rem;
  --code-size: .76rem;
  --icon-size: 18px;
  --pad-y: 56px;
  --pad-x: 30px;
  --pad-bottom: 84px;
  --h1-gap: 30px;
  --h2-gap-top: 64px;
  --h2-gap-bottom: 20px;
  --h3-gap-top: 38px;
  --h3-gap-bottom: 10px;
  --radius: 2px;

  /* Section mark before h2 */
  --mark-w: 2px;
  --mark-h: .82em;
  --mark-gap: .62em;
  --mark-va: -.04em;
  --mark-bg: var(--celadon);

  font-size: var(--base-size);
}

* { box-sizing: border-box; }

html {
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: var(--leading);
  letter-spacing: var(--tracking);
}

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

.wrap {
  max-width: var(--measure);
  margin: 0 auto;
  padding: var(--pad-y) var(--pad-x) var(--pad-bottom);
}

a {
  color: var(--link);
  text-decoration: none;
  border-bottom: 1px solid var(--link-line);
  transition: color .18s ease, border-color .18s ease;
}

a:hover {
  color: var(--link-hover);
  border-bottom-color: var(--link-line-hover);
}

b, strong { font-weight: 600; color: var(--ink-strong); }

/* Reading controls and language switch */
.langbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
  margin-bottom: 46px;
  color: var(--ink-faint);
  font-size: var(--meta-size);
  line-height: 1.6;
  letter-spacing: .12em;
}

.prefs {
  display: flex;
  align-items: center;
  gap: 4px;
}

.prefs { gap: 2px; }

.prefs-sep {
  width: 1px;
  height: 12px;
  margin: 0 8px;
  background: var(--rule);
}

.pref {
  appearance: none;
  margin: 0;
  padding: 4px 6px;
  background: transparent;
  border: 1px solid transparent;
  border-radius: var(--radius);
  color: var(--ink-faint);
  line-height: 0;
  cursor: pointer;
  transition: color .18s ease, background .18s ease, border-color .18s ease;
}

.pref:hover {
  color: var(--ink);
  border-color: var(--rule);
}

.pref[aria-pressed="true"] {
  color: var(--ink-strong);
  background: var(--pref-active-bg);
  border-color: var(--rule);
}

.pref:disabled {
  opacity: .32;
  cursor: default;
}

.pref:focus-visible {
  outline: 1px solid var(--celadon);
  outline-offset: 1px;
}

.ico {
  display: block;
  width: var(--icon-size);
  height: var(--icon-size);
  fill: none;
  stroke: currentColor;
  stroke-width: 1.25;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.lang {
  display: inline-flex;
  padding: 4px 6px;
  color: var(--ink-faint);
  border: 1px solid transparent;
  border-radius: var(--radius);
  transition: color .18s ease, background .18s ease;
}

.lang:hover {
  color: var(--ink);
  background: var(--pref-active-bg);
  border-color: var(--rule);
}

h1 {
  margin: 0 0 var(--h1-gap);
  font-size: var(--h1-size);
  font-weight: 500;
  line-height: 1.38;
  letter-spacing: .035em;
  color: var(--ink-strong);
}

h1::after {
  content: "";
  display: block;
  width: 2.2em;
  height: 1px;
  margin-top: .72em;
  background: var(--h1-rule);
}

h2 {
  margin: var(--h2-gap-top) 0 var(--h2-gap-bottom);
  font-size: var(--h2-size);
  font-weight: 600;
  line-height: 1.6;
  letter-spacing: .08em;
  color: var(--ink-strong);
}

h2::before {
  content: "";
  display: inline-block;
  width: var(--mark-w);
  height: var(--mark-h);
  margin-right: var(--mark-gap);
  vertical-align: var(--mark-va);
  background: var(--mark-bg);
}

h3 {
  margin: var(--h3-gap-top) 0 var(--h3-gap-bottom);
  font-size: var(--h3-size);
  font-weight: 600;
  line-height: 1.7;
  letter-spacing: .04em;
  color: var(--ink-soft);
}

p { margin: 0 0 1.4em; }

ul, ol {
  margin: 0 0 1.5em;
  padding-left: 1.35em;
}

li { margin: .55em 0; }
li::marker { color: var(--celadon); }

img#ide {
  float: right;
  width: 350px;
  max-width: 100%;
  margin: 6px 0 26px 34px;
  padding: 8px;
  background: var(--paper-card);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  aspect-ratio: 800 / 480;
}

.note {
  margin: 2em 0;
  padding: 18px 22px;
  background: var(--note-bg);
  border: 1px solid var(--note-border);
  border-left: 2px solid var(--celadon);
  border-radius: var(--radius);
  color: var(--note-ink);
  font-size: var(--note-size);
  line-height: 1.85;
}

.small {
  font-size: var(--small-size);
  color: var(--ink-faint);
  letter-spacing: .02em;
}

/* Code: a light paper panel instead of a dark slab. */
.cd {
  margin: 20px 0 30px;
  padding: 18px 20px;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  overflow-x: auto;
  color: var(--code-ink);
  font-family: var(--font-mono);
  font-size: var(--code-size);
  line-height: 1.82;
}

.cd .kw { color: var(--code-kw); font-weight: 600; }
.cd .ty { color: var(--code-ty); }
.cd .fn { color: var(--code-fn); }
.cd .st { color: var(--code-st); }
.cd .cm { color: var(--code-cm); font-style: italic; }
.cd .nm { color: var(--code-nm); }
.cd .pr { color: var(--code-pr); }

code {
  font-family: var(--font-mono);
  font-size: .87em;
  color: var(--inline-code-ink);
  background: var(--inline-code-bg);
  padding: .08em .34em;
  border-radius: var(--radius);
}

.btn {
  display: inline-block;
  margin: 8px 8px 8px 0;
  padding: 10px 22px;
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--btn-border);
  border-radius: var(--radius);
  font-size: var(--btn-size);
  font-weight: 500;
  letter-spacing: .08em;
  transition: background .18s ease, border-color .18s ease, color .18s ease;
}

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

.tag {
  display: inline-block;
  margin: 4px 10px 4px 0;
  padding: 1px 8px;
  background: none;
  border: 1px solid var(--tag-rule);
  border-radius: 0;
  color: var(--ink-soft);
  font-size: var(--meta-size);
  letter-spacing: .06em;
}

footer {
  margin-top: 76px;
  padding-top: 18px;
  border-top: 1px solid var(--rule);
  color: var(--ink-faint);
  font-size: var(--meta-size);
  line-height: 1.8;
  letter-spacing: .03em;
}

footer a {
  color: var(--celadon-deep);
  border-bottom: none;
}

footer a:hover { color: var(--ochre); border-bottom: none; }

/* ==========================================================================
   Reading style: plain white, sans-serif, less ornament.
   Only tokens change here; all layout rules above stay shared.
   ========================================================================== */
html[data-style="plain"] {
  --font-body: var(--font-sans);
  --leading: 1.85;
  --tracking: .006em;
  --paper: #FCFCF9;
  --paper-deep: #F5F5F1;
  --paper-card: #FFFFFF;
  --paper-note: #F7F7F3;
  --ink: #353632;
  --ink-strong: #1F211E;
  --ink-soft: #686B64;
  --ink-faint: #8B8E86;
  --rule: #E7E7E0;
  --rule-strong: #CFCFC7;
  --celadon: #8FA09B;
  --celadon-deep: #5F716B;
  --ochre: #9B805F;
  --link-hover: #8B6F4D;
  --h1-rule: #D8D8D0;
  --note-border: #E5E5DE;
  --code-bg: #F1F8FA;
  --code-border: #DDEBEF;
  --pref-active-bg: #F1F1EC;
  --btn-bg-hover: #F1F1EC;
  --tag-rule: #DDDDD6;
  --mark-w: 14px;
  --mark-h: 1px;
  --mark-gap: .56em;
  --mark-va: .18em;
}

html[data-style="plain"] h1,
html[data-style="plain"] h2,
html[data-style="plain"] h3 {
  font-family: inherit;
  letter-spacing: .01em;
}

@media only screen and (max-width: 720px) {
  :root {
    --pad-y: 34px;
    --pad-x: 20px;
    --pad-bottom: 58px;
    --h1-gap: 24px;
    --h2-gap-top: 48px;
    --h3-gap-top: 30px;
  }
  .langbar { margin-bottom: 34px; justify-content: flex-end; gap: 14px; }
  .prefs { order: 2; }
  .lang { order: 1; }
  h1 { font-size: 1.53rem; }
  img#ide {
    float: none;
    display: block;
    width: 100%;
    margin: 0 0 28px;
    padding: 6px;
  }
}