/* =========================================================
   3DGS-SLAM Survey — Light theme, bilingual (EN/中文).
   Switching languages: html[data-lang="en"] hides [lang="zh"],
   and vice versa. Theme remains light in both languages.
   ========================================================= */

:root {
  /* paper-like cream / off-white */
  --bg:            #f7f4ec;
  --bg-elev:       #ffffff;
  --bg-elev-2:     #f0ebde;
  --fg:            #1f242b;
  --fg-mute:       #535d6a;
  --fg-dim:        #8b94a2;

  /* warm-orange splat accent works on light too */
  --accent:        #b8541a;   /* deep warm orange */
  --accent-2:      #1e63c8;   /* solid cool blue */
  --accent-3:      #2c8a3c;   /* clean green */

  --border:        #e0dccd;
  --border-strong: #c8c1ac;
  --code-bg:       #f4efe1;
  --code-fg:       #2a2520;
  --shadow:        0 4px 14px rgba(60,45,25,.08);

  --r:             10px;
  --maxw:          900px;

  --font-sans: ui-sans-serif, system-ui, "Inter", "Segoe UI", Roboto,
               "Noto Sans CJK SC", "PingFang SC", "Source Han Sans SC",
               "Microsoft YaHei", "微软雅黑", sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Consolas, monospace;
  --font-serif: "Charter", "Iowan Old Style", Georgia, "Source Serif Pro", serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; scroll-padding-top: 24px; }

body {
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.72;
  -webkit-font-smoothing: antialiased;
  -webkit-text-size-adjust: 100%;
  overflow-x: hidden;
}

/* ---- Language switching ---- */
html[data-lang="en"] [lang="zh"] { display: none !important; }
html[data-lang="zh"] [lang="en"] { display: none !important; }

/* CJK reads denser; loosen a tad */
html[data-lang="zh"] body { line-height: 1.85; }
html[data-lang="zh"] p,
html[data-lang="zh"] li { letter-spacing: .01em; }
html[data-lang="zh"] code,
html[data-lang="zh"] pre code { letter-spacing: 0; }

/* ---- Layout ---- */
.layout {
  display: grid;
  grid-template-columns: 280px 1fr;
  min-height: 100vh;
}

aside.toc {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow-y: auto;
  background: var(--bg-elev);
  border-right: 1px solid var(--border);
  padding: 24px 20px 60px;
  font-size: 14px;
}
aside.toc .head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 18px;
}
aside.toc h1 {
  font-size: 15px;
  font-weight: 700;
  letter-spacing: .02em;
  color: var(--accent);
  margin: 0 0 6px;
  text-transform: uppercase;
}
aside.toc .sub {
  color: var(--fg-dim);
  font-size: 12px;
  line-height: 1.45;
}
.lang-toggle {
  font-family: var(--font-sans);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .12em;
  color: var(--fg);
  background: var(--bg);
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  padding: 4px 10px;
  cursor: pointer;
  transition: background .15s, color .15s, border-color .15s;
}
.lang-toggle:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

aside.toc nav ul { list-style: none; padding: 0; margin: 0 0 18px; }
aside.toc nav li.h2 { margin: 10px 0 4px; font-weight: 600; color: var(--fg); }
aside.toc nav li.h3 { padding-left: 12px; }
aside.toc nav li.h3 a { color: var(--fg-mute); font-size: 13px; }
aside.toc nav a {
  color: var(--fg);
  text-decoration: none;
  display: block;
  padding: 3px 0;
  border-left: 2px solid transparent;
  padding-left: 8px;
  transition: color .15s, border-color .15s;
}
aside.toc nav a:hover { color: var(--accent); }
aside.toc nav a.active {
  color: var(--accent);
  border-left-color: var(--accent);
  font-weight: 600;
}

main.content {
  padding: 56px 64px 120px;
  max-width: calc(var(--maxw) + 128px);
}
main.content > * { max-width: var(--maxw); }

/* ---- Typography ---- */
h1, h2, h3, h4 { font-family: var(--font-sans); line-height: 1.28; color: #0e1218; }
h1 { font-size: 38px; margin: 0 0 8px; letter-spacing: -.01em; }
h2 { font-size: 28px; margin: 64px 0 12px; border-bottom: 1px solid var(--border); padding-bottom: 8px; }
h3 { font-size: 21px; margin: 36px 0 10px; color: var(--accent-2); }
h4 { font-size: 16px; margin: 22px 0 8px; color: var(--accent); text-transform: uppercase; letter-spacing: .06em; font-weight: 700; }
html[data-lang="zh"] h4 { text-transform: none; letter-spacing: .02em; font-size: 17px; }

p { margin: 0 0 16px; }
a { color: var(--accent-2); text-decoration: none; border-bottom: 1px dotted rgba(30,99,200,.45); }
a:hover { border-bottom-style: solid; }

strong { color: #0e1218; font-weight: 700; }
em { color: var(--accent); font-style: italic; }
html[data-lang="zh"] em { font-style: normal; font-weight: 600; }

code, kbd {
  font-family: var(--font-mono);
  font-size: 13.5px;
}
:not(pre) > code {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 6px;
  color: #8a4a14;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 16px 18px;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.6;
  margin: 18px 0 22px;
  box-shadow: var(--shadow);
  color: var(--code-fg);
}
pre code { color: inherit; }

blockquote {
  border-left: 3px solid var(--accent);
  padding: 4px 16px;
  margin: 16px 0;
  color: var(--fg-mute);
  background: rgba(184,84,26,.05);
  border-radius: 0 var(--r) var(--r) 0;
}

ul, ol { padding-left: 22px; }
li { margin-bottom: 6px; }

/* ---- Hero ---- */
.hero {
  padding: 12px 0 24px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 12px;
}
.hero .eyebrow {
  color: var(--accent);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: .14em;
  font-weight: 700;
  margin-bottom: 14px;
}
html[data-lang="zh"] .hero .eyebrow { text-transform: none; letter-spacing: .04em; }
.hero .sub {
  color: var(--fg-mute);
  font-size: 18px;
  max-width: 740px;
  margin-top: 6px;
}
.hero .meta {
  margin-top: 18px;
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  font-size: 13px;
  color: var(--fg-dim);
}
.hero .meta span::before { content: "▸ "; color: var(--accent); }

/* ---- Callouts ---- */
.callout {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent-2);
  border-radius: var(--r);
  padding: 14px 18px;
  margin: 18px 0;
  box-shadow: var(--shadow);
}
.callout.note    { border-left-color: var(--accent-2); }
.callout.warn    { border-left-color: var(--accent); background: rgba(184,84,26,.04); }
.callout.insight { border-left-color: var(--accent-3); background: rgba(44,138,60,.05); }
.callout .label {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 6px;
}
.callout.warn    .label { color: var(--accent); }
.callout.insight .label { color: var(--accent-3); }
html[data-lang="zh"] .callout .label { text-transform: none; letter-spacing: .04em; font-size: 12px; }

/* ---- Paper cards ---- */
.papergrid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 14px;
  margin: 22px 0;
}
.paper {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 14px 16px;
  transition: transform .15s, border-color .15s, box-shadow .15s;
}
.paper:hover {
  transform: translateY(-2px);
  border-color: var(--accent);
  box-shadow: var(--shadow);
}
.paper .title { font-weight: 700; color: #0e1218; font-size: 15px; margin-bottom: 4px; }
.paper .venue { font-size: 11.5px; color: var(--fg-dim); margin-bottom: 8px; letter-spacing: .03em; }
.paper .desc  { font-size: 13.5px; color: var(--fg-mute); line-height: 1.55; }
.paper .links { margin-top: 8px; font-size: 12px; display: flex; gap: 10px; }
.paper .links a { border: 0; color: var(--accent-2); }

/* ---- Tags ---- */
.tag {
  display: inline-block;
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 999px;
  background: rgba(30,99,200,.10);
  color: var(--accent-2);
  margin-right: 4px;
  margin-bottom: 4px;
  letter-spacing: .03em;
  font-weight: 600;
}
.tag.rgbd    { background: rgba(30,99,200,.10);  color: var(--accent-2); }
.tag.mono    { background: rgba(184,84,26,.12);  color: var(--accent); }
.tag.lidar   { background: rgba(60,45,25,.08);   color: #6b513a; }
.tag.dynamic { background: rgba(200,40,60,.12);  color: #a8243a; }
.tag.semantic{ background: rgba(120,70,170,.12); color: #6e3aa8; }
.tag.feedfwd { background: rgba(44,138,60,.13);  color: var(--accent-3); }
.tag.large   { background: rgba(180,130,40,.14); color: #886414; }

/* ---- Timeline ---- */
.timeline {
  position: relative;
  margin: 24px 0;
  padding-left: 24px;
  border-left: 2px solid var(--border);
}
.timeline .ev {
  position: relative;
  padding: 0 0 22px 18px;
}
.timeline .ev::before {
  content: "";
  position: absolute;
  left: -7px; top: 6px;
  width: 12px; height: 12px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 4px rgba(184,84,26,.18);
}
.timeline .ev.cool::before  { background: var(--accent-2); box-shadow: 0 0 0 4px rgba(30,99,200,.18); }
.timeline .ev.green::before { background: var(--accent-3); box-shadow: 0 0 0 4px rgba(44,138,60,.18); }
.timeline .ev .date { color: var(--fg-dim); font-size: 12px; font-family: var(--font-mono); }
.timeline .ev .ttl  { font-weight: 700; color: #0e1218; font-size: 15px; margin: 2px 0; }
.timeline .ev .desc { color: var(--fg-mute); font-size: 13.5px; }

/* ---- Demo card ---- */
.demo {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 18px;
  margin: 24px 0;
  box-shadow: var(--shadow);
}
.demo h4 { margin-top: 0; }
.demo canvas {
  display: block;
  width: 100%;
  border-radius: 6px;
  background: #1a1d24;          /* dark "screen" embedded in light page */
  cursor: crosshair;
  border: 1px solid var(--border-strong);
}
.demo .controls {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin: 12px 0 6px;
  font-size: 13px;
}
.demo .controls label { color: var(--fg-mute); display: flex; align-items: center; gap: 6px; }
.demo .controls button {
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border-strong);
  border-radius: 6px;
  padding: 6px 12px;
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 13px;
  transition: background .15s, border-color .15s, color .15s;
}
.demo .controls button:hover { border-color: var(--accent); color: var(--accent); }
.demo .controls input[type="range"] { accent-color: var(--accent); }
.demo .legend { font-size: 12.5px; color: var(--fg-dim); margin-top: 8px; line-height: 1.6; }

/* ---- Comparison table ---- */
.cmp {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0;
  font-size: 13.5px;
  background: var(--bg-elev);
  border-radius: var(--r);
  overflow: hidden;
  box-shadow: var(--shadow);
}
.cmp th, .cmp td {
  border-bottom: 1px solid var(--border);
  padding: 9px 12px;
  text-align: left;
  vertical-align: top;
}
.cmp th { color: var(--accent); font-weight: 700; background: rgba(184,84,26,.06); }
.cmp tr:hover td { background: rgba(30,99,200,.03); }
.cmp td code { font-size: 12.5px; }

/* ---- KaTeX sizing ---- */
.katex { font-size: 1.02em !important; }
.katex-display { margin: 16px 0 !important; }

/* ---- Section anchor link ---- */
h2 .anchor, h3 .anchor {
  opacity: 0;
  margin-left: 6px;
  font-size: .65em;
  color: var(--fg-dim);
  border: 0;
  transition: opacity .15s;
}
h2:hover .anchor, h3:hover .anchor { opacity: 1; }

/* ---- Footnotes ---- */
.fn {
  margin-top: 60px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--fg-mute);
}
.fn ol { padding-left: 18px; }

/* ---- Mobile ---- */
@media (max-width: 920px) {
  .layout { grid-template-columns: 1fr; }
  aside.toc {
    position: relative; height: auto; border-right: 0;
    border-bottom: 1px solid var(--border);
    padding: 20px 18px;
  }
  main.content { padding: 28px 22px 80px; }
  h1 { font-size: 30px; }
  h2 { font-size: 24px; margin-top: 44px; }
}

/* ---- Selection ---- */
::selection { background: rgba(184,84,26,.22); color: #0e1218; }

/* ---- Scrollbar (webkit) ---- */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 999px; }
::-webkit-scrollbar-thumb:hover { background: #b3a98e; }

/* ---- Prism (light-theme syntax colors) ---- */
.token.comment, .token.prolog, .token.doctype, .token.cdata { color: #8a9099; font-style: italic; }
.token.punctuation { color: #4a5260; }
.token.property, .token.tag, .token.constant, .token.symbol, .token.deleted { color: #a8243a; }
.token.boolean, .token.number { color: #b8541a; }
.token.selector, .token.attr-name, .token.string, .token.char, .token.builtin, .token.inserted { color: #2c8a3c; }
.token.operator, .token.entity, .token.url, .language-css .token.string, .style .token.string, .token.variable { color: #2a2520; }
.token.atrule, .token.attr-value, .token.keyword { color: #1e63c8; }
.token.function, .token.class-name { color: #6e3aa8; }
.token.regex, .token.important { color: #b8541a; }