:root{
  --bg:#f7f8fa;
  --card:#ffffff;
  --text:#1c1f26;
  --muted:#6b7280;
  --accent:#2563eb;
  --accent-light:#eff6ff;
  --border:#e5e7eb;
  --radius:12px;
}
*{box-sizing:border-box;}
body{
  margin:0;
  font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);
  color:var(--text);
  line-height:1.5;
}
header.site-header{
  background:var(--card);
  border-bottom:1px solid var(--border);
  padding:14px 20px;
}
header.site-header nav{
  max-width:960px;
  margin:0 auto;
  display:flex;
  align-items:center;
  justify-content:space-between;
  flex-wrap:wrap;
  gap:10px;
}
.logo{font-weight:700;font-size:18px;color:var(--accent);text-decoration:none;display:inline-flex;align-items:center;gap:8px;}
.logo img{width:28px;height:28px;border-radius:6px;}
.nav-links{display:flex;gap:16px;flex-wrap:wrap;}
.nav-links a{color:var(--muted);text-decoration:none;font-size:14px;}
.nav-links a:hover{color:var(--accent);}

main{max-width:720px;margin:0 auto;padding:24px 16px 60px;}

h1{font-size:26px;margin-bottom:6px;}
.subtitle{color:var(--muted);margin-bottom:24px;font-size:15px;}

.card{
  background:var(--card);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:24px;
  margin-bottom:20px;
}

.field-row{display:flex;gap:12px;flex-wrap:wrap;margin-bottom:16px;}
.field{flex:1;min-width:130px;}
label{display:block;font-size:13px;font-weight:600;margin-bottom:6px;color:var(--text);}
input, select, textarea{
  width:100%;
  padding:10px 12px;
  border:1px solid var(--border);
  border-radius:8px;
  font-size:15px;
  background:#fff;
  color:var(--text);
  font-family:inherit;
}
textarea{resize:vertical;min-height:140px;}
input:focus, select:focus, textarea:focus{outline:2px solid var(--accent);border-color:var(--accent);}

.unit-toggle{display:flex;gap:8px;margin-bottom:16px;}
.unit-toggle button{
  flex:1;
  padding:8px;
  border:1px solid var(--border);
  background:#fff;
  border-radius:8px;
  cursor:pointer;
  font-size:14px;
}
.unit-toggle button.active{background:var(--accent);color:#fff;border-color:var(--accent);}

.btn, .calc-btn{
  padding:14px;
  background:var(--accent);
  color:#fff;
  border:none;
  border-radius:8px;
  font-size:16px;
  font-weight:600;
  cursor:pointer;
}
.btn:hover, .calc-btn:hover{background:#1d4ed8;}
.calc-btn{width:100%;margin-top:8px;}
.btn.secondary{background:#fff;color:var(--accent);border:1px solid var(--accent);}
.btn.secondary:hover{background:var(--accent-light);}
.btn:disabled{opacity:0.5;cursor:not-allowed;}

.results{display:none;}
.results.show{display:block;}

.result-hero{
  text-align:center;
  padding:20px;
  background:var(--accent-light);
  border-radius:10px;
  margin-bottom:16px;
}
.result-hero .big-num{font-size:36px;font-weight:800;color:var(--accent);}
.result-hero .label{font-size:13px;color:var(--muted);margin-top:4px;}

.grid-3{display:grid;grid-template-columns:1fr 1fr 1fr;gap:10px;}
.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:10px;}
.stat-box{
  border:1px solid var(--border);
  border-radius:8px;
  padding:12px 8px;
  text-align:center;
}
.stat-box .s-title{font-size:12px;color:var(--muted);margin-bottom:4px;}
.stat-box .s-val{font-size:18px;font-weight:700;}

.ad-slot{
  background:#fafafa;
  border:1px dashed var(--border);
  border-radius:10px;
  padding:18px;
  text-align:center;
  color:var(--muted);
  font-size:13px;
  margin:24px 0;
}

.info-section h2{font-size:19px;margin-bottom:8px;}
.info-section p{color:#3a3f47;font-size:15px;margin-bottom:14px;}

.faq-item{margin-bottom:14px;}
.faq-item h3{font-size:15px;margin-bottom:4px;}
.faq-item p{font-size:14px;color:var(--muted);margin:0;}

.disclaimer{
  font-size:12px;
  color:var(--muted);
  border-top:1px solid var(--border);
  padding-top:14px;
  margin-top:10px;
}

.dropzone{
  border:2px dashed var(--border);
  border-radius:10px;
  padding:40px 20px;
  text-align:center;
  color:var(--muted);
  cursor:pointer;
  background:#fff;
}
.dropzone.dragover{border-color:var(--accent);background:var(--accent-light);}
.dropzone input[type=file]{display:none;}

.preview-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:16px;}
.preview-box{text-align:center;}
.preview-box img{max-width:100%;border-radius:8px;border:1px solid var(--border);}
.preview-box .p-label{font-size:12px;color:var(--muted);margin-top:6px;}

.copy-row{display:flex;gap:8px;}
.copy-row input{flex:1;}

footer{
  text-align:center;
  padding:24px 16px;
  color:var(--muted);
  font-size:13px;
  border-top:1px solid var(--border);
}
footer a{color:var(--muted);}

@media (max-width:480px){
  .grid-3{grid-template-columns:1fr 1fr;}
  .preview-grid{grid-template-columns:1fr;}
}