:root {
  --bg: #f3f5f8;
  --surface: #ffffff;
  --surface-2: #f6f8fb;
  --text: #19202a;
  --muted: #5a6677;
  --border: #d9e0e8;
  --accent: #1f6feb;
  --accent-text: #ffffff;
  --focus: #1f6feb;
  --hole: #2b7de9;
  --hole-fill: rgba(43, 125, 233, .22);
  --shaft: #e07a10;
  --shaft-fill: rgba(224, 122, 16, .24);
  --grid: #e3e8ee;
  --clearance: #0e7a4f;
  --clearance-bg: #dcf5e9;
  --transition: #8a5a00;
  --transition-bg: #fdf0cf;
  --interference: #b4232c;
  --interference-bg: #fde3e4;
  --error: #b4232c;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", "Noto Sans CJK SC", "Helvetica Neue", Arial, sans-serif;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12161c;
    --surface: #1a2029;
    --surface-2: #212833;
    --text: #e6ebf2;
    --muted: #9aa7b8;
    --border: #2d3644;
    --accent: #5b9bff;
    --accent-text: #0b1220;
    --focus: #7db0ff;
    --hole: #6aa8ff;
    --hole-fill: rgba(106, 168, 255, .25);
    --shaft: #ffa94d;
    --shaft-fill: rgba(255, 169, 77, .25);
    --grid: #29313d;
    --clearance: #5fdca0;
    --clearance-bg: #12362a;
    --transition: #ffd166;
    --transition-bg: #3a2e0e;
    --interference: #ff8a90;
    --interference-bg: #401a1d;
    --error: #ff8a90;
  }
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
}

.wrap {
  max-width: 880px;
  margin: 0 auto;
  padding: 16px;
}

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

/* header */
.top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 8px 0 16px;
}
.brand { display: flex; align-items: center; gap: 12px; min-width: 0; }
.logo { width: 36px; height: 36px; flex: none; }
h1 { margin: 0; font-size: 1.3rem; line-height: 1.25; letter-spacing: -.01em; }
.sub { margin: 2px 0 0; color: var(--muted); font-size: .88rem; }

.lang {
  display: inline-flex;
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  background: var(--surface);
  flex: none;
}
.lang button {
  font: inherit;
  font-size: .85rem;
  padding: 6px 12px;
  border: 0;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
}
.lang button[aria-pressed="true"] { background: var(--accent); color: var(--accent-text); font-weight: 600; }

/* cards */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
}
.card h2 { margin: 0 0 12px; font-size: 1.05rem; }

/* forms */
.grid-inputs { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.selects { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin-top: 12px; }
.field { min-width: 0; }
label { display: block; font-size: .8rem; color: var(--muted); margin-bottom: 4px; font-weight: 600; }

input, select, .btn {
  font: inherit;
  color: var(--text);
}
input[type="number"], input[type="text"], select {
  width: 100%;
  min-height: 42px;
  padding: 8px 10px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-family: var(--mono);
  font-variant-numeric: tabular-nums;
  font-size: 1rem;
}
input[aria-invalid="true"] { border-color: var(--error); }
.err { min-height: 0; color: var(--error); font-size: .82rem; margin-top: 4px; }
.err:empty { display: none; }

:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; }

/* quick picks */
.quick { margin-top: 16px; }
.quick-title { font-size: .8rem; color: var(--muted); font-weight: 600; margin-bottom: 6px; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  font: inherit;
  font-size: .82rem;
  display: inline-flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 0;
  padding: 6px 10px;
  line-height: 1.3;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface-2);
  color: var(--text);
  cursor: pointer;
  text-align: left;
}
.chip b { font-family: var(--mono); font-size: .92rem; }
.chip span { color: var(--muted); font-size: .75rem; }
.chip:hover { border-color: var(--accent); }
.chip[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: var(--accent-text); }
.chip[aria-pressed="true"] span { color: inherit; opacity: .85; }
.use { margin: 10px 0 0; color: var(--muted); font-size: .88rem; min-height: 1.4em; }
.use:empty { display: none; }

/* results */
.results-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 12px; }
.results-head h2 { margin: 0; }
.badge {
  font-size: .85rem;
  font-weight: 700;
  padding: 4px 12px;
  border-radius: 999px;
  white-space: nowrap;
}
.badge.clearance { color: var(--clearance); background: var(--clearance-bg); }
.badge.transition { color: var(--transition); background: var(--transition-bg); }
.badge.interference { color: var(--interference); background: var(--interference-bg); }

.notice {
  color: var(--error);
  background: var(--interference-bg);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: .92rem;
}

.table-wrap { overflow-x: auto; }
table.data { width: 100%; border-collapse: collapse; font-size: .92rem; }
table.data th, table.data td { padding: 8px 8px; border-bottom: 1px solid var(--border); text-align: right; vertical-align: top; }
table.data th:first-child, table.data td:first-child { text-align: left; color: var(--muted); font-weight: 500; padding-left: 0; }
table.data thead th { font-size: .8rem; color: var(--muted); border-bottom: 2px solid var(--border); }
table.data thead th[data-i18n="hole"] { color: var(--hole); }
table.data thead th[data-i18n="shaft"] { color: var(--shaft); }
table.data td { font-family: var(--mono); font-variant-numeric: tabular-nums; }
table.data td .sub-v { display: block; color: var(--muted); font-size: .8rem; }
table.data td.code { font-weight: 700; }

.clearances { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 16px; }
.metric {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
}
.metric .m-label { font-size: .8rem; color: var(--muted); font-weight: 600; }
.metric .m-val { font-family: var(--mono); font-variant-numeric: tabular-nums; font-size: 1.15rem; font-weight: 700; }
.metric .m-um { font-family: var(--mono); color: var(--muted); font-size: .8rem; }

.summary { margin-top: 16px; }
.summary-label { font-size: .8rem; color: var(--muted); font-weight: 600; margin-bottom: 4px; }
.summary-row { display: flex; gap: 8px; align-items: stretch; }
.summary-text {
  flex: 1;
  min-width: 0;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 10px;
  font-family: var(--mono);
  font-size: .85rem;
  overflow-wrap: anywhere;
  user-select: all;
}
.btn {
  flex: none;
  padding: 0 16px;
  min-height: 42px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: var(--accent-text);
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
}
.btn:hover { filter: brightness(1.08); }

/* diagram */
.diagram { width: 100%; }
.diagram svg { display: block; width: 100%; height: auto; }
.diagram .grid { stroke: var(--grid); stroke-width: 1; }
.diagram .zero { stroke: var(--text); stroke-width: 1.5; }
.diagram .z-hole { fill: var(--hole-fill); stroke: var(--hole); stroke-width: 1.5; }
.diagram .z-shaft { fill: var(--shaft-fill); stroke: var(--shaft); stroke-width: 1.5; }
.diagram text { font-family: var(--mono); font-size: 12px; fill: var(--muted); }
.diagram .halo { paint-order: stroke; stroke: var(--surface); stroke-width: 3px; stroke-linejoin: round; }
.diagram .t-zero { fill: var(--text); font-weight: 700; }
.diagram .t-hole { fill: var(--hole); font-weight: 700; font-size: 13px; }
.diagram .t-shaft { fill: var(--shaft); font-weight: 700; font-size: 13px; }
.diagram .t-dev { fill: var(--text); }
.diagram .empty { color: var(--muted); font-size: .9rem; padding: 24px 0; text-align: center; }

/* about */
.about p, .about li { font-size: .93rem; }
.about ul { padding-left: 1.2em; margin: .4em 0; }
.about p { margin: .5em 0; }
.disclaimer {
  margin-top: 14px;
  padding: 10px 12px;
  border-left: 3px solid var(--transition);
  background: var(--transition-bg);
  border-radius: 4px;
  font-size: .88rem;
}

.foot {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 16px;
  justify-content: space-between;
  color: var(--muted);
  font-size: .85rem;
  padding: 8px 0 24px;
}
.foot a { color: var(--accent); }

@media (max-width: 640px) {
  .selects { grid-template-columns: 1fr 1fr; }
  .grid-inputs { grid-template-columns: 1fr; }
  h1 { font-size: 1.1rem; }
  .sub { display: none; }
  .logo { width: 30px; height: 30px; }
  .clearances { grid-template-columns: 1fr; }
  table.data { font-size: .85rem; }
  table.data th, table.data td { padding: 7px 4px; }
  .summary-row { flex-direction: column; }
  .btn { min-height: 40px; }
}

/* ---- site nav ---- */
.nav { display: flex; gap: 8px; margin: 0 0 16px; flex-wrap: wrap; }
.nav a {
  padding: 7px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-size: .9rem;
  font-weight: 600;
  text-decoration: none;
}
.nav a:hover { border-color: var(--accent); color: var(--text); }
.nav a[aria-current="page"] { background: var(--accent); border-color: var(--accent); color: var(--accent-text); }

/* ---- bolt torque page ---- */
:root {
  --seg-pitch: #0e7a4f;
  --seg-thread: #e07a10;
  --seg-head: #2b7de9;
}
@media (prefers-color-scheme: dark) {
  :root { --seg-pitch: #5fdca0; --seg-thread: #ffa94d; --seg-head: #6aa8ff; }
}
.bolt-inputs { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; }
.bolt-friction { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 12px; margin-top: 12px; }
.hint { color: var(--muted); font-size: .8rem; margin: 6px 0 0; }
.big-row { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.big {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 16px;
}
.big .m-label { font-size: .85rem; color: var(--muted); font-weight: 600; }
.big .big-val { font-family: var(--mono); font-variant-numeric: tabular-nums; font-size: 2rem; font-weight: 700; line-height: 1.2; }
.big .big-val small { font-size: .95rem; font-weight: 600; color: var(--muted); margin-left: 4px; }
.sec-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 12px; margin-top: 12px; }
.sec-grid .metric .m-val { font-size: 1rem; }
.breakdown { margin-top: 20px; }
.breakdown h3, .ref-title { margin: 0 0 8px; font-size: .95rem; }
.stack { display: flex; height: 28px; border-radius: 8px; overflow: hidden; border: 1px solid var(--border); background: var(--surface-2); }
.stack > span { display: block; min-width: 0; }
.seg-pitch { background: var(--seg-pitch); }
.seg-thread { background: var(--seg-thread); }
.seg-head { background: var(--seg-head); }
.legend { list-style: none; margin: 10px 0 0; padding: 0; display: flex; flex-wrap: wrap; gap: 6px 16px; font-size: .88rem; }
.legend li { display: flex; align-items: center; gap: 6px; }
.legend i { width: 12px; height: 12px; border-radius: 3px; flex: none; }
.legend b { font-family: var(--mono); font-variant-numeric: tabular-nums; }
.ref-wrap { overflow-x: auto; max-height: 420px; overflow-y: auto; }
table.ref { width: 100%; border-collapse: collapse; font-size: .92rem; }
table.ref th, table.ref td { padding: 7px 8px; border-bottom: 1px solid var(--border); text-align: right; font-variant-numeric: tabular-nums; }
table.ref th:first-child, table.ref td:first-child { text-align: left; }
table.ref thead th { position: sticky; top: 0; background: var(--surface); font-size: .8rem; color: var(--muted); border-bottom: 2px solid var(--border); }
table.ref td { font-family: var(--mono); }
table.ref tbody tr { cursor: pointer; }
table.ref tbody tr:hover { background: var(--surface-2); }
table.ref tbody tr.sel { background: var(--accent); color: var(--accent-text); font-weight: 700; }
table.ref tbody tr.sel td { border-color: var(--accent); }
.about h3 { font-size: .95rem; margin: 1em 0 .2em; }
.about code { font-family: var(--mono); font-size: .88em; background: var(--surface-2); padding: 1px 5px; border-radius: 4px; overflow-wrap: anywhere; }

@media (max-width: 640px) {
  .bolt-inputs { grid-template-columns: 1fr 1fr; }
  .bolt-friction { grid-template-columns: 1fr 1fr; }
  .bolt-friction .field:first-child { grid-column: 1 / -1; }
  .sec-grid { grid-template-columns: 1fr 1fr; }
  .big .big-val { font-size: 1.6rem; }
  .big { padding: 12px; }
}

/* 中文界面加载前隐藏页面，防止先闪一下英文（见页面头部的内联脚本） */
html.i18n-pending body { visibility: hidden; }