/* ============================================================
   Laser / ILCA 帆船图解指南  —  Blueprint Design System
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;500;600&family=IBM+Plex+Sans:wght@400;500;600;700&family=IBM+Plex+Sans+SC:wght@400;500;600;700&display=swap');

:root {
  /* ---- ink + paper ---- */
  --bg:        #071d33;          /* deep navy ground */
  --bg-2:      #0a2745;          /* card / panel */
  --bg-3:      #0d2e52;          /* raised panel */
  --grid:      rgba(122,176,224,0.10);
  --grid-bold: rgba(122,176,224,0.18);

  /* ---- line work ---- */
  --line:      #8fc1e8;          /* primary blueprint stroke */
  --line-dim:  #3f6b97;          /* secondary stroke / construction */
  --line-faint:#27496e;

  /* ---- type ---- */
  --ink:       #e3eefa;          /* headings / strong */
  --ink-2:     #b9d2ea;          /* body */
  --ink-3:     #7fa3c4;          /* muted / captions */

  /* ---- functional accents (color-coded, not decorative) ---- */
  --wind:      #ffd166;          /* amber — wind / important */
  --force:     #ff7a59;          /* coral — applied forces */
  --water:     #4cc9c0;          /* teal — water / hydro-forces */

  --maxw: 1120px;

  --mono: 'IBM Plex Mono', ui-monospace, monospace;
  --sans: 'IBM Plex Sans', 'IBM Plex Sans SC', system-ui, sans-serif;
  --zh:   'IBM Plex Sans SC', 'IBM Plex Sans', system-ui, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background-color: var(--bg);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 28px 28px;
  color: var(--ink-2);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* faint vignette so the grid recedes at the edges */
body::before {
  content: "";
  position: fixed; inset: 0;
  pointer-events: none;
  background: radial-gradient(120% 90% at 50% 0%, transparent 55%, rgba(3,12,22,0.55) 100%);
  z-index: 0;
}

/* ---------- layout primitives ---------- */
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 28px; position: relative; z-index: 1; }

section.block {
  padding: 76px 0 60px;
  border-top: 1px solid var(--line-faint);
}
section.block:first-of-type { border-top: none; }

/* ---------- mono helpers ---------- */
.mono { font-family: var(--mono); }
.tick {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--ink-3);
}

/* corner-tick frame used on figures + cards */
.frame {
  position: relative;
  background: var(--bg-2);
  border: 1px solid var(--line-faint);
}
.frame::before, .frame::after {
  content: ""; position: absolute; width: 10px; height: 10px;
  border: 1px solid var(--line); border-bottom: none; border-right: none;
  top: 7px; left: 7px;
}
.frame::after { top: auto; left: auto; bottom: 7px; right: 7px;
  border: 1px solid var(--line); border-top: none; border-left: none; }

/* ============================================================
   HERO
   ============================================================ */
.hero { padding: 92px 0 64px; position: relative; }
.hero .kicker { color: var(--wind); }
.hero h1 {
  font-family: var(--sans);
  font-weight: 700;
  font-size: clamp(40px, 7vw, 86px);
  line-height: 0.98;
  letter-spacing: -0.02em;
  color: var(--ink);
  margin: 18px 0 6px;
}
.hero h1 .zh { font-family: var(--zh); display: block; font-size: 0.46em; font-weight: 600; color: var(--line); letter-spacing: 0; margin-top: 14px; }
.hero .lede {
  max-width: 720px; margin-top: 22px; font-size: 18px; color: var(--ink-2);
}
.hero .lede .zh { font-family: var(--zh); display:block; margin-top: 8px; color: var(--ink-3); font-size: 16px; }

.spec-row {
  display: flex; flex-wrap: wrap; gap: 10px; margin-top: 30px;
}
.spec {
  font-family: var(--mono); font-size: 12px; letter-spacing: 0.08em;
  color: var(--line); border: 1px solid var(--line-faint);
  padding: 7px 12px; background: rgba(143,193,232,0.04);
}
.spec b { color: var(--ink); font-weight: 600; }

/* ---------- table of contents ---------- */
.toc {
  margin-top: 44px;
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px;
  background: var(--line-faint); border: 1px solid var(--line-faint);
}
.toc a {
  background: var(--bg-2); padding: 16px 16px 18px; text-decoration: none;
  color: var(--ink-2); transition: background .15s, color .15s; display: block;
}
.toc a:hover { background: var(--bg-3); color: var(--ink); }
.toc a .no { font-family: var(--mono); font-size: 12px; color: var(--wind); letter-spacing: 0.1em; }
.toc a .t  { display: block; margin-top: 8px; font-weight: 600; color: var(--ink); font-size: 15px; }
.toc a .z  { display: block; font-family: var(--zh); font-size: 13px; color: var(--ink-3); margin-top: 2px; }

/* ============================================================
   SECTION HEADINGS
   ============================================================ */
.sec-head { display: flex; align-items: baseline; gap: 18px; margin-bottom: 8px; }
.sec-head .no {
  font-family: var(--mono); font-size: 14px; letter-spacing: 0.2em;
  color: var(--wind); padding-top: 6px;
}
.sec-head h2 {
  margin: 0; font-size: clamp(26px, 3.4vw, 38px); font-weight: 700;
  color: var(--ink); letter-spacing: -0.01em; line-height: 1.05;
}
.sec-head h2 .zh { font-family: var(--zh); font-weight: 600; }
.sec-sub { color: var(--ink-3); max-width: 760px; margin: 0 0 38px; }
.sec-sub .zh { font-family: var(--zh); display:block; margin-top: 4px; }

/* ============================================================
   BILINGUAL TEXT BLOCK  (EN | 中文, parallel)
   ============================================================ */
.bil { display: grid; grid-template-columns: 1fr 1fr; gap: 0 34px; }
.bil > .en, .bil > .zh { margin: 0; }
.bil > .en { color: var(--ink-2); }
.bil > .zh { font-family: var(--zh); color: var(--ink-2); }
.bil + .bil { margin-top: 14px; }

/* dividing hairline between the two languages */
.bil.ruled { position: relative; }
.bil.ruled::before {
  content:""; position: absolute; top: 2px; bottom: 2px; left: calc(50% - 17px);
  border-left: 1px dashed var(--line-faint);
}

/* ============================================================
   FIGURE (svg diagrams)
   ============================================================ */
figure.fig { margin: 0; }
.fig-stage {
  padding: 26px; background: var(--bg-2); border: 1px solid var(--line-faint);
  position: relative; overflow: hidden;
}
.fig-stage svg { display: block; width: 100%; height: auto; }
figcaption {
  font-family: var(--mono); font-size: 12px; letter-spacing: 0.05em;
  color: var(--ink-3); padding: 12px 4px 0; display:flex; gap: 10px;
}
figcaption .fig-no { color: var(--wind); }

/* svg label conventions */
.lbl-en { font: 600 13px var(--mono, monospace); fill: var(--ink); }
.lbl-zh { font: 500 13px var(--zh, sans-serif); fill: var(--line); }
.lbl-sm { font: 500 11px var(--mono, monospace); fill: var(--ink-3); }

/* ============================================================
   PARTS TABLE
   ============================================================ */
.parts { margin-top: 36px; border: 1px solid var(--line-faint); }
.parts .row {
  display: grid; grid-template-columns: 44px 1.1fr 1fr 2.2fr;
  border-top: 1px solid var(--line-faint);
}
.parts .row:first-child { border-top: none; }
.parts .row.head {
  background: var(--bg-3); font-family: var(--mono); font-size: 11px;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-3);
}
.parts .row.head > div { padding: 11px 14px; }
.parts .row > div { padding: 14px; border-left: 1px solid var(--line-faint); }
.parts .row > div:first-child { border-left: none; }
.parts .num { font-family: var(--mono); color: var(--wind); font-size: 13px; }
.parts .en  { color: var(--ink); font-weight: 600; }
.parts .en small { display:block; font-weight: 400; color: var(--ink-3); font-family: var(--mono); font-size: 11px; letter-spacing: 0.04em; margin-top: 3px; }
.parts .zhn { font-family: var(--zh); color: var(--ink); font-weight: 500; }
.parts .fn  { color: var(--ink-2); font-size: 15px; }
.parts .fn .zh { font-family: var(--zh); display:block; color: var(--ink-3); margin-top: 4px; }
.parts .row:hover { background: rgba(143,193,232,0.04); }

/* ============================================================
   STEP CARDS  (rigging / capsize)
   ============================================================ */
.steps { display: grid; grid-template-columns: repeat(2, 1fr); gap: 22px; margin-top: 34px; }
.step { border: 1px solid var(--line-faint); background: var(--bg-2); display:flex; flex-direction: column; }
.step .step-fig { padding: 18px 18px 6px; border-bottom: 1px dashed var(--line-faint); }
.step .step-fig svg { display:block; width: 100%; height: auto; }
.step .step-fig img.knot { display:block; width: 100%; height: 188px; object-fit: contain; background: var(--bg-3); border-radius: 6px; }
.step .step-body { padding: 16px 18px 20px; }
.step .step-no {
  font-family: var(--mono); font-size: 12px; letter-spacing: 0.16em; color: var(--wind);
  display:flex; align-items:center; gap: 10px; margin-bottom: 10px;
}
.step .step-no::after { content:""; flex:1; border-top: 1px solid var(--line-faint); }
.step h4 { margin: 0 0 3px; color: var(--ink); font-size: 17px; font-weight: 600; }
.step h4 .zh { font-family: var(--zh); display:block; font-size: 15px; color: var(--line); font-weight: 500; margin-top: 2px; }
.step p { margin: 10px 0 0; font-size: 14.5px; }
.step p.zh { font-family: var(--zh); color: var(--ink-3); }

/* ============================================================
   CALLOUT / NOTE
   ============================================================ */
.note {
  margin-top: 26px; border-left: 3px solid var(--wind);
  background: rgba(255,209,102,0.06); padding: 16px 20px;
}
.note.warn { border-left-color: var(--force); background: rgba(255,122,89,0.07); }
.note .tag { font-family: var(--mono); font-size: 11px; letter-spacing: 0.16em; text-transform: uppercase; color: var(--wind); }
.note.warn .tag { color: var(--force); }
.note p { margin: 6px 0 0; font-size: 15px; }
.note p.zh { font-family: var(--zh); color: var(--ink-3); margin-top: 4px; }

/* ============================================================
   TWO-COLUMN FIGURE+TEXT
   ============================================================ */
.split { display: grid; grid-template-columns: 1.15fr 1fr; gap: 34px; align-items: start; margin-top: 30px; }
.split.flip { grid-template-columns: 1fr 1.15fr; }
.split .txt h3 { color: var(--ink); font-size: 19px; margin: 0 0 4px; font-weight: 600; }
.split .txt h3 .zh { font-family: var(--zh); display:block; font-size: 15px; color: var(--line); font-weight: 500; }
.split .txt .pair { margin-top: 18px; }
.split .txt .pair .en { color: var(--ink-2); margin: 0; }
.split .txt .pair .zh { font-family: var(--zh); color: var(--ink-3); margin: 5px 0 0; font-size: 15px; }

/* legend chips for vector colors */
.legend { display:flex; flex-wrap: wrap; gap: 8px 16px; margin-top: 16px; }
.legend .k { display:flex; align-items:center; gap: 8px; font-family: var(--mono); font-size: 12px; color: var(--ink-3); }
.legend .k i { width: 22px; height: 0; border-top: 3px solid var(--line); display:inline-block; }
.legend .k.wind i  { border-color: var(--wind); }
.legend .k.force i { border-color: var(--force); }
.legend .k.water i { border-color: var(--water); }
.legend .k.line  i { border-color: var(--line); }

/* ============================================================
   SVG DRAWING CONVENTIONS (shared by all diagrams)
   ============================================================ */
svg .s-line  { stroke: var(--line);     fill: none; stroke-width: 2; stroke-linejoin: round; stroke-linecap: round; }
svg .s-dim   { stroke: var(--line-dim); fill: none; stroke-width: 1.4; stroke-linecap: round; }
svg .s-faint { stroke: var(--line-faint);fill: none; stroke-width: 1; }
svg .s-wind  { stroke: var(--wind);     fill: none; stroke-width: 2.4; stroke-linecap: round; }
svg .s-force { stroke: var(--force);    fill: none; stroke-width: 2.6; stroke-linecap: round; }
svg .s-water { stroke: var(--water);    fill: none; stroke-width: 2.4; stroke-linecap: round; }
svg .dash    { stroke-dasharray: 6 6; }
svg .dash-sm { stroke-dasharray: 3 4; }
svg .sail    { fill: rgba(143,193,232,0.09); stroke: var(--line); stroke-width: 2; stroke-linejoin: round; }
svg .hull    { fill: rgba(13,46,82,0.9); stroke: var(--line); stroke-width: 2.2; stroke-linejoin: round; }
svg .water-fill { fill: rgba(76,201,192,0.06); }
svg .f-line  { fill: var(--line); }
svg .f-wind  { fill: var(--wind); }
svg .f-force { fill: var(--force); }
svg .f-water { fill: var(--water); }
svg .f-ink   { fill: var(--ink); }
/* callout number badge */
svg .badge   { fill: var(--bg); stroke: var(--wind); stroke-width: 1.6; }
svg .badge-t { fill: var(--wind); font: 600 13px var(--mono, monospace); text-anchor: middle; }
svg .lead    { stroke: var(--line-dim); stroke-width: 1; stroke-dasharray: 2 3; fill: none; }
/* on-figure name labels */
svg text.figlab { font: 600 12.5px var(--mono, monospace); fill: var(--ink); }
svg text.figlab tspan { font-family: var(--zh, sans-serif); font-weight: 500; fill: var(--line); }
svg text.figlab tspan.n { font-family: var(--mono, monospace); font-weight: 600; fill: var(--wind); }

/* knot diagrams: rope shaded standing→working, with over/under casing */
svg .rope  { fill: none; stroke-width: 9; stroke-linecap: round; stroke-linejoin: round; }
svg .cased { fill: none; stroke: var(--bg-2); stroke-width: 17; stroke-linecap: round; }
svg .post2 { fill: var(--bg-3); stroke: var(--line-dim); stroke-width: 5; }

/* ============================================================
   GLOSSARY
   ============================================================ */
.glossary { margin-top: 30px; display: grid; grid-template-columns: 1fr 1fr; gap: 1px; background: var(--line-faint); border: 1px solid var(--line-faint); }
.glossary .term { background: var(--bg-2); padding: 15px 20px; }
.glossary .term:hover { background: var(--bg-3); }
.glossary .term .t { color: var(--ink); font-weight: 600; font-size: 16px; }
.glossary .term .t .zh { font-family: var(--zh); color: var(--line); font-weight: 500; font-size: 14px; margin-left: 8px; }
.glossary .term .d { color: var(--ink-3); font-size: 14px; margin-top: 6px; line-height: 1.5; }
.glossary .term .d .zh { font-family: var(--zh); display: block; margin-top: 2px; }
@media (max-width: 720px){ .glossary { grid-template-columns: 1fr; } }

/* ============================================================
   FOOTER
   ============================================================ */
footer { border-top: 1px solid var(--line-faint); padding: 40px 0 70px; color: var(--ink-3); }
footer .mono { font-size: 12px; letter-spacing: 0.1em; }
footer .zh { font-family: var(--zh); }

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 880px) {
  body { font-size: 16px; }
  .toc { grid-template-columns: repeat(2, 1fr); }
  .bil { grid-template-columns: 1fr; gap: 4px; }
  .bil.ruled::before { display: none; }
  .bil > .zh { color: var(--ink-3); padding-bottom: 4px; }
  .steps { grid-template-columns: 1fr; }
  .split, .split.flip { grid-template-columns: 1fr; }
  .parts .row { grid-template-columns: 34px 1fr 1fr; }
  .parts .row .fn { grid-column: 1 / -1; border-left: none; border-top: 1px dashed var(--line-faint); }
  .parts .row.head .fn { display: none; }
}
@media (max-width: 520px) {
  .wrap { padding: 0 18px; }
  .toc { grid-template-columns: 1fr; }
}