:root{
  --bg:#f7f8fb;
  --surface:#ffffff;
  --text:#172033;
  --muted:#667085;
  --line:#e5e7eb;
  --primary:#2563eb;
  --primary-dark:#1d4ed8;
  --soft:#eff6ff;
  --success:#15803d;
  --danger:#b42318;
  --max:1120px;
  --radius:16px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;
  color:var(--text);
  background:var(--bg);
  line-height:1.65;
}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%}
.container{width:min(var(--max),calc(100% - 32px));margin:auto}
.site-header{
  background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20;
}
.nav{height:68px;display:flex;align-items:center;justify-content:space-between;gap:24px}
.logo{font-weight:800;font-size:20px;color:var(--text);letter-spacing:-.03em}
.logo span{color:var(--primary)}
.nav-links{display:flex;gap:18px;align-items:center}
.nav-links a{color:#475467;font-size:14px;font-weight:600}
.menu-btn{display:none;border:1px solid var(--line);background:#fff;border-radius:10px;padding:8px 10px}
.hero{padding:72px 0 58px;background:linear-gradient(180deg,#fff 0%,#f7f8fb 100%)}
.hero-grid{display:grid;grid-template-columns:1.3fr .7fr;gap:42px;align-items:center}
.eyebrow{display:inline-flex;background:var(--soft);color:var(--primary);padding:6px 10px;border-radius:999px;font-size:12px;font-weight:800}
h1{font-size:clamp(38px,6vw,64px);line-height:1.05;letter-spacing:-.05em;margin:16px 0}
h2{font-size:30px;line-height:1.2;letter-spacing:-.03em;margin:0 0 12px}
h3{font-size:20px;line-height:1.3;margin:0 0 8px}
.lead{font-size:19px;color:var(--muted);max-width:680px}
.hero-card{background:#fff;border:1px solid var(--line);border-radius:24px;padding:24px;box-shadow:0 16px 40px rgba(16,24,40,.07)}
.problem-list{display:grid;gap:10px;margin-top:18px}
.problem{display:block;padding:13px 14px;border:1px solid var(--line);border-radius:12px;color:var(--text);background:#fff;font-weight:700}
.problem:hover{border-color:#bfdbfe;background:#f8fbff;text-decoration:none}
.section{padding:58px 0}
.section-head{display:flex;justify-content:space-between;gap:20px;align-items:end;margin-bottom:22px}
.muted{color:var(--muted)}
.grid{display:grid;gap:18px}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-2{grid-template-columns:repeat(2,1fr)}
.card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:22px}
.card:hover{box-shadow:0 8px 28px rgba(16,24,40,.06)}
.card p{color:var(--muted);margin:6px 0 0}
.tag{display:inline-block;font-size:11px;font-weight:800;color:#475467;background:#f2f4f7;border-radius:999px;padding:4px 8px;margin-bottom:12px}
.tool-card{display:flex;flex-direction:column;min-height:190px}
.tool-card .button{margin-top:auto}
.button{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  border:0;border-radius:10px;background:var(--primary);color:#fff;
  padding:10px 15px;font-weight:800;cursor:pointer;font-size:14px;
}
.button:hover{background:var(--primary-dark);text-decoration:none}
.button.secondary{background:#eef2f6;color:#344054}
.button.secondary:hover{background:#e4e7ec}
.center{text-align:center}
.cta{background:#0f172a;color:#fff;border-radius:24px;padding:38px}
.cta p{color:#cbd5e1}
.breadcrumbs{padding:22px 0;font-size:13px;color:var(--muted)}
.page{padding:20px 0 70px}
.prose{max-width:800px}
.prose h1{font-size:42px}
.prose h2{font-size:27px;margin-top:34px}
.prose h3{margin-top:24px}
.prose p,.prose li{color:#475467}
.prose ul{padding-left:22px}
.note{border-left:4px solid var(--primary);background:var(--soft);padding:14px 16px;border-radius:8px}
.tool-shell{background:#fff;border:1px solid var(--line);border-radius:20px;padding:24px}
.dropzone{border:2px dashed #cbd5e1;border-radius:16px;padding:38px 20px;text-align:center;background:#f8fafc;cursor:pointer}
.dropzone.drag{border-color:var(--primary);background:var(--soft)}
.file-input{display:none}
.controls{display:grid;gap:14px;grid-template-columns:repeat(2,1fr);margin-top:18px}
.control label{display:block;font-size:13px;font-weight:800;margin-bottom:6px}
input[type="number"],select,input[type="text"]{
  width:100%;border:1px solid #d0d5dd;border-radius:10px;padding:10px 12px;font:inherit;background:#fff;
}
.range-row{display:flex;align-items:center;gap:12px}
input[type="range"]{width:100%}
.preview{display:grid;grid-template-columns:1fr 1fr;gap:18px;margin-top:22px}
.preview-box{background:#f8fafc;border:1px solid var(--line);border-radius:12px;padding:12px;text-align:center}
.preview-box img{max-height:320px;object-fit:contain}
.result{margin-top:18px;padding:14px;border-radius:12px;background:#f0fdf4;color:#166534;display:none}
.error{margin-top:18px;padding:14px;border-radius:12px;background:#fef3f2;color:var(--danger);display:none}
.footer{background:#fff;border-top:1px solid var(--line);padding:34px 0;margin-top:20px}
.footer-inner{display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap}
.footer-links{display:flex;gap:15px;flex-wrap:wrap;font-size:14px}
.small{font-size:13px}
.stat{font-size:28px;font-weight:900}
.faq{border-top:1px solid var(--line);padding:18px 0}
.faq summary{font-weight:800;cursor:pointer}
.search-box{display:flex;gap:10px;margin:18px 0 26px}
.search-box input{flex:1}
@media(max-width:820px){
  .nav-links{display:none;position:absolute;top:68px;left:0;right:0;background:#fff;border-bottom:1px solid var(--line);padding:14px 16px;flex-direction:column;align-items:flex-start}
  .nav-links.open{display:flex}
  .menu-btn{display:block}
  .hero-grid{grid-template-columns:1fr}
  .grid-3{grid-template-columns:1fr}
  .grid-2{grid-template-columns:1fr}
  .controls,.preview{grid-template-columns:1fr}
  .section-head{display:block}
}

/* V1 AdSense-ready content helpers */
.ad-slot{min-height:90px;border:1px dashed #d0d5dd;border-radius:12px;background:#fafafa;color:#98a2b3;display:flex;align-items:center;justify-content:center;font-size:11px;letter-spacing:.04em;text-transform:uppercase;margin:28px 0}.ad-slot span{padding:0 10px}.answer-box{background:#f8fbff;border:1px solid #bfdbfe;border-radius:16px;padding:20px 22px;margin:22px 0}.answer-box strong{display:block;font-size:13px;text-transform:uppercase;letter-spacing:.04em;color:var(--primary);margin-bottom:7px}.related{margin-top:36px}.link-list{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.link-list a{display:block;background:#fff;border:1px solid var(--line);border-radius:12px;padding:13px 15px;font-weight:700}.check-list{padding-left:20px}.tool-meta{display:flex;gap:8px;flex-wrap:wrap;margin:14px 0}.pill{display:inline-block;border-radius:999px;background:#f2f4f7;padding:5px 9px;font-size:12px;font-weight:700;color:#475467}.prose .lead{margin-bottom:8px}.notice{background:#fffbeb;border:1px solid #f5d77a;padding:14px 16px;border-radius:10px}.trust-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.trust-grid .card{min-height:150px}@media(max-width:820px){.link-list,.trust-grid{grid-template-columns:1fr}}

/* V1 AdSense-ready content helpers */
.ad-slot{min-height:90px;border:1px dashed #d0d5dd;border-radius:12px;background:#fafafa;color:#98a2b3;display:flex;align-items:center;justify-content:center;font-size:11px;letter-spacing:.04em;text-transform:uppercase;margin:28px 0}.ad-slot span{padding:0 10px}.answer-box{background:#f8fbff;border:1px solid #bfdbfe;border-radius:16px;padding:20px 22px;margin:22px 0}.answer-box strong{display:block;font-size:13px;text-transform:uppercase;letter-spacing:.04em;color:var(--primary);margin-bottom:7px}.related{margin-top:36px}.link-list{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.link-list a{display:block;background:#fff;border:1px solid var(--line);border-radius:12px;padding:13px 15px;font-weight:700}.check-list{padding-left:20px}.tool-meta{display:flex;gap:8px;flex-wrap:wrap;margin:14px 0}.pill{display:inline-block;border-radius:999px;background:#f2f4f7;padding:5px 9px;font-size:12px;font-weight:700;color:#475467}.prose .lead{margin-bottom:8px}.notice{background:#fffbeb;border:1px solid #f5d77a;padding:14px 16px;border-radius:10px}.trust-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.trust-grid .card{min-height:150px}@media(max-width:820px){.link-list,.trust-grid{grid-template-columns:1fr}}

/* V1 AdSense-ready content helpers */
.ad-slot{min-height:90px;border:1px dashed #d0d5dd;border-radius:12px;background:#fafafa;color:#98a2b3;display:flex;align-items:center;justify-content:center;font-size:11px;letter-spacing:.04em;text-transform:uppercase;margin:28px 0}.ad-slot span{padding:0 10px}.answer-box{background:#f8fbff;border:1px solid #bfdbfe;border-radius:16px;padding:20px 22px;margin:22px 0}.answer-box strong{display:block;font-size:13px;text-transform:uppercase;letter-spacing:.04em;color:var(--primary);margin-bottom:7px}.related{margin-top:36px}.link-list{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.link-list a{display:block;background:#fff;border:1px solid var(--line);border-radius:12px;padding:13px 15px;font-weight:700}.check-list{padding-left:20px}.tool-meta{display:flex;gap:8px;flex-wrap:wrap;margin:14px 0}.pill{display:inline-block;border-radius:999px;background:#f2f4f7;padding:5px 9px;font-size:12px;font-weight:700;color:#475467}.prose .lead{margin-bottom:8px}.notice{background:#fffbeb;border:1px solid #f5d77a;padding:14px 16px;border-radius:10px}.trust-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.trust-grid .card{min-height:150px}@media(max-width:820px){.link-list,.trust-grid{grid-template-columns:1fr}}

/* V1 AdSense-ready content helpers */
.ad-slot{min-height:90px;border:1px dashed #d0d5dd;border-radius:12px;background:#fafafa;color:#98a2b3;display:flex;align-items:center;justify-content:center;font-size:11px;letter-spacing:.04em;text-transform:uppercase;margin:28px 0}.ad-slot span{padding:0 10px}.answer-box{background:#f8fbff;border:1px solid #bfdbfe;border-radius:16px;padding:20px 22px;margin:22px 0}.answer-box strong{display:block;font-size:13px;text-transform:uppercase;letter-spacing:.04em;color:var(--primary);margin-bottom:7px}.related{margin-top:36px}.link-list{display:grid;grid-template-columns:repeat(2,1fr);gap:10px}.link-list a{display:block;background:#fff;border:1px solid var(--line);border-radius:12px;padding:13px 15px;font-weight:700}.check-list{padding-left:20px}.tool-meta{display:flex;gap:8px;flex-wrap:wrap;margin:14px 0}.pill{display:inline-block;border-radius:999px;background:#f2f4f7;padding:5px 9px;font-size:12px;font-weight:700;color:#475467}.prose .lead{margin-bottom:8px}.notice{background:#fffbeb;border:1px solid #f5d77a;padding:14px 16px;border-radius:10px}.trust-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.trust-grid .card{min-height:150px}@media(max-width:820px){.link-list,.trust-grid{grid-template-columns:1fr}}

/* V1.2 problem-solving experience */
.problem-solver{background:#f8fafc;border:1px solid var(--line);border-radius:18px;padding:24px;margin-top:20px}.problem-buttons{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:16px}.problem-choice{border:1px solid var(--line);background:#fff;border-radius:12px;padding:14px;text-align:left;font:inherit;font-weight:700;cursor:pointer}.problem-choice:hover{border-color:#98a2b3;transform:translateY(-1px)}.solver-result{margin-top:18px;background:#fff;border:1px solid #bfdbfe;border-radius:14px;padding:18px}.solver-result[hidden]{display:none}.solver-result h3{margin:0 0 8px}.target-grid{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:18px}.target-side{border:1px solid var(--line);border-radius:14px;padding:18px;background:#fff}.target-side label{font-weight:700;display:block;margin-bottom:7px}.target-side input,.target-side select{width:100%;padding:10px 11px;border:1px solid #d0d5dd;border-radius:9px;background:#fff}.target-note{font-size:13px;color:#667085;margin-top:8px}.tool-shell + .prose{margin-top:28px}@media(max-width:820px){.problem-buttons,.target-grid{grid-template-columns:1fr}}