* { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --bg: #fafafa;
  --card: #ffffff;
  --text: #222222;
  --muted: #666666;
  --faint: #999999;
  --border: #e8eefb;
  --border-strong: #b3c6ef;
  --accent: #2563eb;
  --accent-text: #ffffff;
  --green: #2e7d32;
  --red: #c62828;
  --blue: #1565c0;
  --amber: #e65100;
  --shadow: rgba(0,0,0,0.04);
  --header-grad: linear-gradient(135deg, #2563eb, #3b82f6);
}
[data-theme="dark"] {
  --bg: #16181c;
  --card: #23272d;
  --text: #e8e8e8;
  --muted: #b2b5ba;
  --faint: #8b8f96;
  --border: #2a313d;
  --border-strong: #3d4a66;
  --accent: #3b82f6;
  --accent-text: #ffffff;
  --green: #7bc47f;
  --red: #ef9a9a;
  --blue: #90caf9;
  --amber: #ffb74d;
  --shadow: rgba(0,0,0,0.35);
  --header-grad: linear-gradient(135deg, #1e40af, #2563eb);
}
body {
  font-family: -apple-system, "PingFang SC", "Segoe UI", "Microsoft YaHei", "Noto Sans", sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  transition: background 0.2s, color 0.2s;
}
.container { width: 100%; max-width: 760px; padding: 0 20px; }

.site-header {
  width: 100%;
  background: var(--header-grad);
  border-bottom: 1px solid rgba(255,255,255,0.15);
  padding: 14px 0;
  position: sticky; top: 0; z-index: 10;
}
.header-inner { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin: 0 auto; }
.back { color: #ffffff; text-decoration: none; font-size: 14px; }
.back:hover { text-decoration: underline; }
.controls { display: flex; gap: 8px; align-items: center; }
.controls button,
.controls select {
  padding: 6px 12px;
  border: 1px solid rgba(255,255,255,0.45);
  background: rgba(255,255,255,0.15);
  color: #ffffff;
  border-radius: 8px;
  cursor: pointer;
  font-size: 13px;
}
.controls select option { color: #222222; }

main.container { padding-top: 20px; padding-bottom: 40px; }

.crumbs { font-size: 13px; color: var(--faint); margin-bottom: 10px; }
.crumbs a { color: var(--accent); text-decoration: none; }
.crumbs a:hover { text-decoration: underline; }

h1 { font-size: 22px; font-weight: 700; margin-bottom: 18px; }

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
  width: 100%;
  margin-bottom: 20px;
  box-shadow: 0 2px 8px var(--shadow);
}

.field { margin-bottom: 14px; }
.field label { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.row { display: flex; gap: 10px; align-items: flex-end; }
.row .field { flex: 1; margin-bottom: 0; }
.row .grow { flex: 1; }
.row .fixed { flex: none; }
.row .fixed select { width: auto; min-width: 84px; }

input, select {
  padding: 10px 12px;
  border: 1px solid var(--border-strong);
  border-radius: 8px;
  font-size: 16px;
  background: var(--card);
  color: var(--text);
  width: 100%;
}
input:focus, select:focus { outline: none; border-color: var(--accent); }
input[type="color"] {
  padding: 4px;
  height: 48px;
  width: 100%;
  cursor: pointer;
  border-radius: 8px;
}

.btn {
  width: 100%;
  padding: 12px;
  background: var(--accent);
  color: var(--accent-text);
  border: none;
  border-radius: 8px;
  font-size: 16px;
  cursor: pointer;
}
.btn:hover { opacity: 0.85; }
.btn.ghost {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--border-strong);
}

.hint { color: var(--faint); font-size: 13px; text-align: center; margin-top: 6px; }

/* 结果块 */
.result-box {
  margin-top: 18px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  text-align: center;
}
.result-box .big {
  font-size: 34px;
  font-weight: 700;
  line-height: 1.2;
}
.result-box .sub { color: var(--muted); font-size: 14px; margin-top: 4px; }
.badge {
  display: inline-block;
  margin-top: 10px;
  padding: 5px 14px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 600;
  color: #fff;
}
.badge.under { background: var(--blue); }
.badge.normal { background: var(--green); }
.badge.over { background: var(--amber); }
.badge.obese { background: var(--red); }

/* RGB 颜色工具 */
.swatch {
  height: 80px;
  border-radius: 10px;
  border: 1px solid var(--border-strong);
  margin-bottom: 16px;
  transition: background 0.15s;
}
.rgb-field { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.rgb-field .ch {
  width: 22px; font-weight: 700; text-align: center; flex: none;
}
.rgb-field input[type="range"] { flex: 1; }
.rgb-field input[type="number"] { width: 74px; flex: none; }
.color-output { font-size: 14px; color: var(--muted); margin-top: 4px; }
.color-output b { color: var(--text); font-family: ui-monospace, monospace; }

/* 计算器 */
.calc-display {
  background: var(--bg);
  border: 1px solid var(--border-strong);
  border-radius: 10px;
  padding: 14px 16px;
  text-align: right;
  margin-bottom: 14px;
  min-height: 76px;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.calc-display .expr {
  font-size: 20px;
  color: var(--muted);
  min-height: 24px;
  word-break: break-all;
  font-family: ui-monospace, monospace;
}
.calc-display .result {
  font-size: 30px;
  font-weight: 700;
  word-break: break-all;
}
.calc-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
}
.calc-grid .key {
  padding: 14px 6px;
  font-size: 17px;
  border: 1px solid var(--border-strong);
  background: var(--card);
  color: var(--text);
  border-radius: 10px;
  cursor: pointer;
  text-align: center;
}
.calc-grid .key:hover { border-color: var(--accent); }
.calc-grid .key.op { color: var(--accent); font-weight: 600; }
.calc-grid .key.fn { color: var(--blue); font-size: 15px; }
.calc-grid .key.eq {
  background: var(--accent);
  color: var(--accent-text);
  font-weight: 700;
}
.calc-grid .key.danger { color: var(--red); }
.calc-grid .key.span2 { grid-column: span 2; }
.calc-toolbar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
}
.calc-toolbar button {
  padding: 6px 12px;
  font-size: 13px;
  border: 1px solid var(--border-strong);
  background: var(--card);
  color: var(--text);
  border-radius: 8px;
  cursor: pointer;
}
.calc-toolbar .active { background: var(--accent); color: var(--accent-text); }

/* 小费按钮 */
.tip-grid { display: flex; flex-wrap: wrap; gap: 8px; }
.tip-grid button {
  flex: 1;
  min-width: 56px;
  padding: 10px;
  border: 1px solid var(--border-strong);
  background: var(--card);
  color: var(--text);
  border-radius: 8px;
  cursor: pointer;
  font-size: 14px;
}
.tip-grid button.active { background: var(--accent); color: var(--accent-text); }

/* 结果行 */
.result-line {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  padding: 8px 0;
  border-bottom: 1px solid var(--border);
  font-size: 15px;
}
.result-line:last-child { border-bottom: none; }
.result-line .k { color: var(--muted); }
.result-line .v { font-weight: 600; font-variant-numeric: tabular-nums; }

/* 相关工具（纵向排列） */
.related h2 { font-size: 16px; margin-bottom: 14px; }
.links { display: flex; flex-direction: column; }
.links a {
  display: block;
  font-size: 14px;
  color: var(--text);
  text-decoration: none;
  padding: 9px 4px;
  border-bottom: 1px solid var(--border);
}
.links a:last-child { border-bottom: none; }
.links a:hover { color: var(--accent); background: var(--bg); }

/* 响应式 */
@media (max-width: 640px) {
  .container { padding: 0 14px; }
  h1 { font-size: 19px; }
  .card { padding: 18px; }
  .row { flex-direction: column; align-items: stretch; }
}