/* ======================================================================
   自行车齿比计算 · 独立设计（机械工坊：钢青 + 荧光黄绿）
   浅色 = 车间白；深色 = 夜骑暗调（由导航主题开关控制）
   ====================================================================== */
.bgr{
  --ink:#172931; --sub:#4d6873; --faint:#94adb6;
  --bg:#eef3f4; --card:#ffffff; --card2:#e8eff1; --line:#d2e0e4; --line2:#e2ecee;
  --pri:#2f6d86; --pri-2:#4a92ad; --pri-soft:#dcecf1; --pri-ink:#245668;
  --acc:#8fae0c; --acc-soft:#eef2d3; --acc-ink:#6b8407;
  --ok:#0f7a4d; --ok-soft:#dcf3e8; --warn:#9a6a06; --warn-soft:#fdf1d8; --red:#c22a32; --red-soft:#fbe7e8;
  --r:18px;
  --shadow:0 1px 2px rgba(23,41,49,.06),0 14px 34px rgba(47,109,134,.13);
  color:var(--ink);
  font-family:"HarmonyOS Sans SC","PingFang SC","Microsoft YaHei",system-ui,sans-serif;
  font-size:15px; line-height:1.78;
  background:
    radial-gradient(880px 380px at 10% -160px, rgba(47,109,134,.12), transparent 62%),
    radial-gradient(720px 320px at 92% -120px, rgba(143,174,12,.10), transparent 60%),
    var(--bg);
  padding:0 16px 56px;
}
:root[data-theme="dark"] .bgr{
  --ink:#e6f1f4; --sub:#a2c0ca; --faint:#5f7f89;
  --bg:#0a1519; --card:#122228; --card2:#1a3038; --line:#274552; --line2:#1f3a45;
  --pri:#5fb0c9; --pri-2:#84c9de; --pri-soft:rgba(95,176,201,.15); --pri-ink:#b3e2f0;
  --acc:#c6e04a; --acc-soft:rgba(198,224,74,.14); --acc-ink:#dcef86;
  --ok:#4ade80; --ok-soft:rgba(74,222,128,.13); --warn:#fbbf24; --warn-soft:rgba(251,191,36,.13); --red:#f87171; --red-soft:rgba(248,113,113,.14);
  --shadow:0 1px 2px rgba(0,0,0,.5),0 14px 34px rgba(0,0,0,.5);
}
.bgr *{box-sizing:border-box;}
.bgr b{font-weight:700;}
.bgr-wrap{max-width:1120px;margin:0 auto;}
.bgr code,.bgr output{font-family:"JetBrains Mono",ui-monospace,SFMono-Regular,Consolas,monospace;}

/* ---------- Hero：牙盘 + 飞轮 + 链条 ---------- */
.bgr-hero{margin-top:10px;border:1px solid var(--line);border-radius:22px;background:var(--card);box-shadow:var(--shadow);padding:26px 30px;display:flex;gap:30px;align-items:center;flex-wrap:wrap;}
.bgr-gears{flex:none;width:190px;height:140px;position:relative;}
.bgr-ring{position:absolute;left:8px;top:14px;width:104px;height:104px;border-radius:50%;border:10px dashed var(--pri);background:var(--card2);animation:bgrspin 12s linear infinite;}
.bgr-hub{position:absolute;left:50%;top:50%;width:26px;height:26px;border-radius:50%;transform:translate(-50%,-50%);background:var(--pri);}
.bgr-cog{position:absolute;right:16px;bottom:18px;width:58px;height:58px;border-radius:50%;border:7px dashed var(--acc);background:var(--card2);animation:bgrspin 6.7s linear infinite;}
.bgr-cog-hub{position:absolute;left:50%;top:50%;width:14px;height:14px;border-radius:50%;transform:translate(-50%,-50%);background:var(--acc);}
.bgr-chain{position:absolute;left:60px;top:40px;width:96px;height:3px;background:repeating-linear-gradient(90deg,var(--sub) 0 5px,transparent 5px 9px);transform:rotate(24deg);}
@keyframes bgrspin{to{transform:rotate(360deg);}}
.bgr-gear-num{position:absolute;left:60px;top:66px;transform:translateX(-50%);z-index:3;font-size:12.5px;font-weight:900;color:#fff;background:var(--pri);border-radius:999px;padding:2px 12px;white-space:nowrap;box-shadow:var(--shadow);}
.bgr-hero-txt{flex:1;min-width:280px;}
.bgr-hero h1{margin:0 0 6px;font-size:clamp(23px,3.3vw,31px);font-weight:900;letter-spacing:-.01em;}
.bgr-hero h1 span{background:linear-gradient(92deg,var(--pri),var(--acc));-webkit-background-clip:text;background-clip:text;color:transparent;}
.bgr-hero p{margin:0;color:var(--sub);font-size:14.5px;max-width:740px;}
.bgr-hero p em{font-style:normal;color:var(--pri-ink);font-weight:700;}
.bgr-quick{display:flex;flex-wrap:wrap;gap:8px;margin-top:12px;}
.bgr-qchip{border:1px dashed var(--pri-2);background:var(--pri-soft);color:var(--pri-ink);border-radius:999px;padding:5px 14px;font-size:12.5px;font-weight:700;cursor:pointer;transition:all .15s;}
.bgr-qchip:hover{background:var(--pri);color:#fff;border-style:solid;}
:root[data-theme="dark"] .bgr-qchip:hover{color:#122228;}

/* ---------- 卡片与通用控件 ---------- */
.bgr-card{background:var(--card);border:1px solid var(--line);border-radius:var(--r);box-shadow:var(--shadow);padding:18px 20px;margin-top:18px;}
.bgr-card h2{margin:0 0 4px;font-size:16.5px;font-weight:800;display:flex;align-items:center;gap:8px;}
.bgr-card h2 .bgr-num{display:inline-flex;align-items:center;justify-content:center;width:23px;height:23px;border-radius:8px;background:linear-gradient(135deg,var(--pri),var(--acc));color:#fff;font-size:12px;font-weight:900;flex:none;}
:root[data-theme="dark"] .bgr-card h2 .bgr-num{color:#122228;}
.bgr-sub{margin:16px 0 6px;font-size:14px;font-weight:800;color:var(--pri-ink);}
.bgr-tip{font-size:12.8px;color:var(--sub);margin:0 0 12px;}
.bgr-tip em{font-style:normal;color:var(--pri-ink);font-weight:700;}
.bgr-row{display:flex;flex-wrap:wrap;gap:8px;align-items:center;margin:10px 0;}
.bgr-btn{border:none;border-radius:12px;padding:9px 18px;font-size:14px;font-weight:800;cursor:pointer;transition:all .15s;}
.bgr-btn-go{background:linear-gradient(135deg,var(--pri),var(--acc));color:#fff;box-shadow:0 6px 16px rgba(47,109,134,.3);}
.bgr-btn-go:hover{filter:brightness(1.07);}
.bgr-btn-ghost{background:var(--card2);color:var(--pri-ink);border:1px solid var(--line);}
.bgr-btn-ghost:hover{border-color:var(--pri-2);}
.bgr-msg{margin-top:10px;font-size:13px;min-height:20px;font-weight:600;}
.bgr-msg.err{color:var(--red);}
.bgr-msg.ok{color:var(--ok);}

/* ---------- 表单 ---------- */
.bgr-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-top:6px;}
@media (max-width:820px){.bgr-grid{grid-template-columns:1fr;}}
.bgr-field label{display:block;font-size:12.5px;font-weight:700;color:var(--sub);margin-bottom:5px;}
.bgr-field input,.bgr-field select,.bgr-area{width:100%;border:1px solid var(--line);border-radius:11px;background:var(--card2);color:var(--ink);padding:9px 12px;font-size:14px;font-weight:600;font-family:inherit;transition:border-color .15s;}
.bgr-field input:focus,.bgr-field select:focus,.bgr-area:focus{outline:none;border-color:var(--pri-2);box-shadow:0 0 0 3px var(--pri-soft);}
.bgr-field-wide{margin-top:12px;}
.bgr-field-btn{display:flex;align-items:flex-end;}
.bgr-field-btn .bgr-btn{width:100%;}
.bgr-area{margin-top:4px;resize:vertical;font-family:"JetBrains Mono",ui-monospace,Consolas,monospace;font-size:13px;line-height:1.7;}

/* ---------- 表格 ---------- */
.bgr-scroll{overflow-x:auto;border:1px solid var(--line2);border-radius:14px;}
.bgr-table{width:100%;border-collapse:collapse;font-size:13.5px;min-width:600px;}
.bgr-table th{background:var(--card2);color:var(--sub);font-weight:800;text-align:left;padding:9px 12px;white-space:nowrap;border-bottom:1px solid var(--line);}
.bgr-table td{padding:9px 12px;border-bottom:1px solid var(--line2);white-space:nowrap;}
.bgr-table tbody tr:last-child td{border-bottom:none;}
.bgr-table tbody tr:hover td{background:var(--pri-soft);}
.bgr-table code{color:var(--pri-ink);font-weight:700;}
.bgr-cad{min-width:auto;text-align:center;}
.bgr-cad th,.bgr-cad td{text-align:center;}
.bgr-cad td{font-family:"JetBrains Mono",ui-monospace,Consolas,monospace;font-weight:800;color:var(--pri-ink);}

/* ---------- 结果 ---------- */
.bgr-result{margin-top:14px;border:1px solid var(--line);border-radius:16px;background:linear-gradient(150deg,var(--pri-soft),var(--card2));padding:16px 18px;}
.bgr-res-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;}
@media (max-width:820px){.bgr-res-grid{grid-template-columns:repeat(2,1fr);}}
.bgr-res-cell{background:var(--card);border:1px solid var(--line2);border-radius:12px;padding:10px 14px;}
.bgr-res-cell h4{margin:0 0 4px;font-size:12.5px;color:var(--sub);font-weight:800;}
.bgr-res-cell p{margin:0;font-size:clamp(16px,2.4vw,20px);font-weight:900;color:var(--pri-ink);font-family:"JetBrains Mono",ui-monospace,Consolas,monospace;}
.bgr-res-cell small{display:block;font-size:11.5px;color:var(--sub);font-weight:500;margin-top:3px;}
.bgr-note{margin-top:12px;font-size:13px;font-weight:600;color:var(--sub);border-left:3px solid var(--pri-2);padding:2px 0 2px 12px;}

/* ---------- 反推输出 ---------- */
.bgr-revout{margin-top:14px;border:1px dashed var(--pri-2);border-radius:14px;background:var(--card2);padding:14px 16px;font-size:14px;font-weight:700;color:var(--pri-ink);}
.bgr-revout small{display:block;font-weight:500;color:var(--sub);font-size:12.5px;margin-top:4px;}

/* ---------- 批量统计 ---------- */
.bgr-stat{margin-top:10px;font-size:13px;color:var(--sub);font-weight:600;min-height:20px;}
.bgr-stat b.err{color:var(--red);}

/* ---------- 摘要 ---------- */
.bgr-sum{margin:6px 0 4px;border:1px dashed var(--line);border-radius:12px;background:var(--card2);color:var(--ink);padding:12px 15px;font-size:13px;line-height:1.8;white-space:pre-wrap;word-break:break-all;font-family:"JetBrains Mono",ui-monospace,Consolas,monospace;max-height:260px;overflow:auto;}

@media (max-width:860px){
  .bgr-hero{padding:20px 18px;gap:18px;}
  .bgr-card{padding:15px 14px;}
}