:root{
  --bg:#f4f6fa;
  --card:#ffffff;
  --ink:#1c2733;
  --ink-soft:#5b6b7b;
  --line:#e3e9f0;
  --brand:#0f5c8a;
  --brand-2:#13739f;
  --brand-soft:#e7f1f7;
  --accent:#e0861c;
  --accent-soft:#fdf1e0;
  --ok:#1f7a52;
  --ok-soft:#e6f4ec;
  --warn:#b3572a;
  --radius:14px;
  --shadow:0 10px 30px rgba(15,60,110,.10);
  --header-h:64px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg);
  color:var(--ink);
  font-family:"Segoe UI",system-ui,-apple-system,"Helvetica Neue",Arial,"PingFang SC","Microsoft YaHei","Noto Sans CJK SC","Hiragino Sans",sans-serif;
  font-size:16px;
  line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--brand);text-decoration:none}
a:hover{text-decoration:underline}

/* ===== Header ===== */
.site-header{
  position:sticky;top:0;z-index:100;
  background:linear-gradient(90deg,#0d4a70,#11628f);
  color:#fff;
  box-shadow:0 2px 10px rgba(0,0,0,.15);
}
.header-inner{
  max-width:1200px;margin:0 auto;padding:0 20px;
  height:var(--header-h);
  display:flex;align-items:center;gap:18px;flex-wrap:nowrap;
}
.brand{display:flex;align-items:center;gap:10px;white-space:nowrap}
.brand .logo{
  width:36px;height:36px;border-radius:9px;
  background:#fff;display:flex;align-items:center;justify-content:center;
  color:var(--brand);font-weight:800;font-size:18px;
}
.brand .brand-name{font-weight:700;font-size:17px;letter-spacing:.3px}
.header-nav{display:flex;align-items:center;gap:6px;margin-left:auto;overflow-x:auto;-webkit-overflow-scrolling:touch}
.header-nav .navlink{
  color:#eaf4fb;font-size:14.5px;padding:8px 11px;border-radius:8px;white-space:nowrap;
  display:flex;align-items:center;gap:6px;transition:background .15s;
}
.header-nav .navlink:hover{background:rgba(255,255,255,.14);text-decoration:none}
.header-nav .navlink.active{background:rgba(255,255,255,.2);color:#fff;font-weight:600}
.header-actions{display:flex;align-items:center;gap:8px}
.lang-select{
  appearance:none;-webkit-appearance:none;
  background-color:#ffffff;color:#0c3d5c;border:1px solid rgba(255,255,255,.35);
  border-radius:8px;padding:7px 26px 7px 10px;font-size:14px;font-weight:600;cursor:pointer;
  background-image:url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='10' height='6'><path d='M1 1l4 4 4-4' stroke='%230c3d5c' stroke-width='1.8' fill='none'/></svg>");
  background-repeat:no-repeat;background-position:right 8px center;
  box-shadow:0 1px 4px rgba(0,0,0,.18);
}
.lang-select option{color:var(--ink);background:#fff}
.ghost-btn{
  background:#ffffff;border:1px solid rgba(255,255,255,.35);color:#0c3d5c;
  border-radius:8px;padding:7px 12px;font-size:13.5px;cursor:pointer;white-space:nowrap;
  display:inline-flex;align-items:center;gap:6px;transition:background .15s,color .15s;
  box-shadow:0 1px 4px rgba(0,0,0,.18);
}
.ghost-btn svg{width:15px;height:15px}
.ghost-btn:hover{background:#e9f3fb;text-decoration:none;color:#08334d}
.ghost-btn svg{width:15px;height:15px}

/* ===== Layout ===== */
.page{max-width:1200px;margin:0 auto;padding:28px 20px 60px}
.breadcrumb{font-size:13.5px;color:var(--ink-soft);margin-bottom:6px}
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);padding:26px;margin-bottom:22px;
}
.page-title{font-size:28px;margin:4px 0 6px;color:var(--ink);display:flex;align-items:center;gap:12px}
.page-title .ico{font-size:30px}
.page-sub{color:var(--ink-soft);max-width:820px;margin:0 0 8px}
.lead{color:var(--ink-soft);font-size:15px}

/* button */
.btn{display:inline-flex;align-items:center;gap:8px;border:none;cursor:pointer;
  border-radius:9px;padding:12px 22px;font-size:15.5px;font-weight:600;
  transition:transform .05s,background .15s;color:#fff;background:var(--brand-2)}
.btn:hover{background:var(--brand);text-decoration:none}
.btn:active{transform:translateY(1px)}
.btn.secondary{background:#eef2f7;color:var(--ink);border:1px solid var(--line)}
.btn.secondary:hover{background:#e2e8f0}

/* form */
.form-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:18px}
.field{display:flex;flex-direction:column;gap:6px}
.field label{font-size:13.5px;font-weight:600;color:var(--ink)}
.field .hint{font-size:12.5px;color:var(--ink-soft)}
.formula{margin-top:8px;padding:10px 12px;border:1px dashed var(--line);border-radius:10px;background:#f7fafc;font-size:13px}
.formula .f-label{font-weight:700;color:var(--brand);font-size:12px;text-transform:uppercase;letter-spacing:.4px;margin-bottom:5px}
.formula .f-line{font-family:Cambria,Georgia,"Times New Roman",serif;font-style:italic;font-size:15px;color:var(--ink);margin:4px 0}
.formula .f-note{font-size:12px;color:var(--ink-soft);margin-top:2px}
.copy-btn{margin-left:8px;border:1px solid var(--line);background:#fff;border-radius:7px;padding:1px 8px;cursor:pointer;font-size:13px;line-height:1.5;color:var(--ink-soft);vertical-align:middle;transition:all .15s}
.copy-btn:hover{background:var(--brand-soft);color:var(--brand);border-color:var(--brand-2)}
.copy-btn.copied{color:var(--ok);border-color:var(--ok)}
.alpha-io{margin-top:10px;padding-top:10px;border-top:1px dashed var(--line)}
.alpha-io .ai-label{font-weight:600;color:var(--ink);font-size:13px;margin-bottom:8px}
.alpha-io .ai-row{display:flex;gap:8px;flex-wrap:wrap;align-items:flex-end}
.alpha-io .ai-in{display:flex;flex-direction:column;gap:3px;min-width:96px}
.alpha-io .ai-cap{font-size:11px;color:var(--ink-soft)}
.alpha-io .ai-in input{width:100%;padding:7px 8px;border:1px solid var(--line);border-radius:7px;font-size:14px;background:#fbfcfe;color:var(--ink)}
.alpha-io .ai-out{margin-top:8px;font-size:13px;color:var(--brand);font-weight:600}
.alpha-io .ai-btn{height:32px;padding:0 12px;font-size:13px}
.formula .units{margin-top:10px;padding-top:10px;border-top:1px dashed var(--line)}
.formula .units .f-label2{font-weight:700;color:var(--brand);font-size:12px;text-transform:uppercase;letter-spacing:.4px;margin-bottom:5px}
.ai-tbar{display:flex;align-items:center;justify-content:space-between;gap:8px;flex-wrap:wrap;margin-bottom:10px}
.ai-usr{display:inline-flex;align-items:center;gap:6px;font-size:12px;color:var(--ink-soft)}
.ai-usr select{padding:6px 8px;border:1px solid var(--line);border-radius:7px;font-size:13px;background:#fbfcfe;color:var(--ink);cursor:pointer}
.ai-prefill{display:flex;align-items:center;gap:6px;font-size:12px;color:var(--ink-soft);margin-bottom:8px}
.ai-prefill select{flex:1;max-width:240px;padding:6px 8px;border:1px solid var(--line);border-radius:7px;font-size:13px;background:#fbfcfe;color:var(--ink);cursor:pointer}
.warn-box{margin-top:14px;padding:10px 12px;border-radius:8px;background:#fff7e6;border:1px solid #f2c14e;color:#7a5a04;font-size:13.5px;line-height:1.5}
.sec-title{margin:34px 0 12px;font-size:20px;color:var(--ink);display:flex;align-items:center;gap:8px}
.field .select-wrap{position:relative}
input[type=number],input[type=text],select,textarea{
  width:100%;padding:11px 13px;border:1px solid var(--line);border-radius:9px;
  font-size:15px;font-family:inherit;background:#fbfcfe;color:var(--ink);
  transition:border .15s,box-shadow .15s;
}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--brand-2);box-shadow:0 0 0 3px rgba(19,115,159,.14)}
input[readonly]{background:#eef2f7;font-weight:600}
.unit-input{position:relative}
.unit-input input{padding-right:52px}
.unit-input .unit{position:absolute;right:12px;top:50%;transform:translateY(-50%);color:var(--ink-soft);font-size:13px}
.inline-check{display:flex;align-items:center;gap:8px;font-size:14.5px;font-weight:500}

/* segmented */
.segmented{display:inline-flex;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:#f2f5f9}
.segmented button{border:none;background:transparent;padding:10px 18px;font-size:14px;cursor:pointer;color:var(--ink-soft)}
.segmented button.on{background:var(--brand-2);color:#fff;font-weight:600}

/* result */
.result-box{margin-top:22px;border:1px solid var(--brand-soft);background:linear-gradient(180deg,#f4fafd,#fff);
  border-radius:12px;padding:20px;display:none}
.result-box.show{display:block;animation:fadein .25s ease}
@keyframes fadein{from{opacity:0;transform:translateY(4px)}to{opacity:1;transform:none}}
.result-box h3{margin:0 0 12px;font-size:16px;color:var(--brand);display:flex;align-items:center;gap:8px}
.result-kpis{display:grid;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));gap:14px}
.kpi{background:#fff;border:1px solid var(--line);border-radius:10px;padding:14px 16px}
.kpi .k-label{font-size:12.5px;color:var(--ink-soft);text-transform:none}
.kpi .k-value{font-size:22px;font-weight:700;color:var(--ink);margin-top:2px}
.kpi .k-value small{font-size:13px;font-weight:500;color:var(--ink-soft)}
.kpi .k-note{font-size:12.5px;color:var(--ink-soft);margin-top:2px}
.kpi.primary .k-value{color:var(--brand)}
.kpi.warn .k-value{color:var(--warn)}
.kpi.ok .k-value{color:var(--ok)}

/* note / formula */
.note{margin-top:18px;font-size:13.5px;color:var(--ink-soft);background:#fbfcfe;border-left:3px solid var(--brand-soft);
  padding:12px 16px;border-radius:0 8px 8px 0}
.formula{background:#0f2740;color:#d9ecf7;border-radius:10px;padding:14px 18px;font-family:Consolas,"Courier New",monospace;
  font-size:16px;margin:14px 0;overflow-x:auto;white-space:pre-wrap}
.formula b{color:#ffd38a}

/* ===== Home ===== */
.hero{padding:54px 20px 40px;text-align:center;background:linear-gradient(160deg,#0d4a70,#11628f 60%,#149bb3);
  color:#fff;border-radius:16px;margin-bottom:34px}
.hero h1{font-size:34px;margin:0 0 12px}
.hero p{max-width:760px;margin:0 auto 6px;color:#dff0f9;font-size:16px}
.hero .badges{display:flex;flex-wrap:wrap;gap:10px;justify-content:center;margin-top:20px}
.badge{background:rgba(255,255,255,.16);border:1px solid rgba(255,255,255,.25);border-radius:999px;padding:6px 14px;font-size:13px}
.tools-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:22px}
.tool-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:24px;
  box-shadow:var(--shadow);display:flex;flex-direction:column;transition:transform .15s,box-shadow .15s}
.tool-card:hover{transform:translateY(-3px);box-shadow:0 16px 38px rgba(15,60,110,.16)}
.tool-card .tc-ico{font-size:30px}
.tool-card h3{margin:12px 0 8px;font-size:18.5px;color:var(--ink)}
.tool-card p{color:var(--ink-soft);font-size:14.5px;margin:0 0 16px;flex:1}
.tool-card .tc-link{color:var(--brand-2);font-weight:600;font-size:14.5px}

/* ===== Materials table ===== */
.table-wrap{overflow-x:auto;border:1px solid var(--line);border-radius:12px}
table.data{width:100%;border-collapse:collapse;background:#fff;font-size:14px;min-width:860px}
table.data th,table.data td{padding:11px 13px;border-bottom:1px solid var(--line);text-align:left;vertical-align:top}
table.data thead th{background:var(--brand);color:#fff;font-weight:600;font-size:13px;position:sticky;top:var(--header-h)}
table.data tbody tr:nth-child(even){background:#f7fafc}
table.data tbody tr:hover{background:var(--brand-soft)}
table.data td.num{text-align:right;white-space:nowrap}
.color-dot{display:inline-block;width:10px;height:10px;border-radius:3px;margin-right:6px}

/* legend */
.legend{display:flex;flex-wrap:wrap;gap:14px;margin-top:14px;font-size:13px;color:var(--ink-soft)}

/* footer */
.site-footer{background:#0d1f2e;color:#9db4c4;border-top:4px solid var(--brand);padding:30px 20px;font-size:13.5px}
.footer-inner{max-width:1200px;margin:0 auto;display:flex;flex-wrap:wrap;gap:24px;justify-content:space-between;align-items:center}
.site-footer a{color:#d6e6f2}

@media (max-width:860px){
  .header-inner{flex-wrap:wrap;height:auto;padding:10px 14px;gap:8px}
  .site-header{position:static}
  .header-nav{order:4;width:100%;margin:0}
  .page{padding:20px 14px 44px}
  .hero h1{font-size:26px}
  .hero{padding:36px 16px 30px}
  .page-title{font-size:23px}
}

/* ---------- toolbar (report / share) ---------- */
.toolbar{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-bottom:18px}
.toolbar .btn{font-size:13.5px}

/* ---------- engineering report overlay ---------- */
.report-overlay{position:fixed;inset:0;background:rgba(15,34,58,.45);display:none;align-items:flex-start;justify-content:center;padding:28px 14px;z-index:1000;overflow:auto}
.report-overlay.open{display:flex}
.report-card{background:#fff;border-radius:14px;max-width:760px;width:100%;box-shadow:0 18px 60px rgba(0,0,0,.28)}
.report-toolbar{display:flex;gap:10px;justify-content:flex-end;padding:14px 18px;border-bottom:1px solid var(--line);position:sticky;top:0;background:#fff;border-radius:14px 14px 0 0;z-index:2}
.report-body{padding:20px 22px 28px;font-family:Cambria,Georgia,"Times New Roman",serif;color:#1c2b3a}
.report-body h2{font-size:22px;margin:0 0 4px}
.r-sub{color:#5a6b7c;font-size:12.5px;margin-bottom:10px;font-family:var(--sans,inherit)}
.r-mat{margin-bottom:14px;font-size:14px}
.r-table{width:100%;border-collapse:collapse;margin-bottom:18px;font-size:13.5px;font-family:var(--sans,inherit)}
.r-table caption{text-align:left;font-weight:700;color:#0f5c8a;font-size:12px;text-transform:uppercase;letter-spacing:.04em;margin:6px 0 4px}
.r-table td{border-bottom:1px solid #e4ebf1;padding:7px 6px;vertical-align:top}
.r-table td:first-child{color:#57697c;width:46%}
.r-table td:last-child{font-weight:500}
.r-table td b{color:#0f2d4a}
.r-unit{color:#8a97a5;font-size:12px}
.r-foot{margin-top:6px;padding-top:12px;border-top:1px solid #e4ebf1;color:#7a8896;font-size:11.5px;font-family:var(--sans,inherit)}

/* ---------- printing only the open report ---------- */
@media print{
  body > *:not(#reportOverlay){display:none !important}
  #reportOverlay{position:static;display:block;background:none;padding:0;overflow:visible}
  .report-card{box-shadow:none;max-width:100%}
  .report-toolbar{display:none !important}
}