:root{
  --blue:#1d4ed8; --purple:#7c3aed; --ink:#1e293b; --muted:#64748b;
  --bg:#f8fafc; --card:#fff; --green:#16a34a; --red:#dc2626; --amber:#b45309;
  --line:#e2e8f0;
}
*{box-sizing:border-box;margin:0;padding:0}
body{font-family:system-ui,-apple-system,"Segoe UI",Roboto,Arial,sans-serif;background:var(--bg);color:var(--ink);line-height:1.6}
.wrap{max-width:980px;margin:0 auto;padding:0 20px}
.site-header{background:linear-gradient(135deg,var(--blue),var(--purple));color:#fff;padding:14px 0}
.header-inner{display:flex;align-items:center;justify-content:space-between;gap:12px}
.back{color:#fff;text-decoration:none;opacity:.9;font-size:.9rem}
.back:hover{opacity:1;text-decoration:underline}
.brand{display:flex;align-items:center;gap:8px;font-size:1.05rem}
.brand-mark{font-size:1.4rem}
.hero{padding:36px 0 8px}
.hero h1{font-size:1.9rem;margin-bottom:10px;line-height:1.25}
.lede{color:var(--muted);font-size:1.02rem;max-width:720px}
.card{background:var(--card);border-radius:16px;box-shadow:0 4px 24px rgba(15,23,42,.07);padding:28px;margin:24px 0}
.dropzone{border:2px dashed #c7d2fe;background:#eef2ff;border-radius:14px;padding:40px 20px;text-align:center;cursor:pointer;transition:border-color .15s,background .15s}
.dropzone:hover,.dropzone.dragover{border-color:var(--blue);background:#e0e9ff}
.dz-icon{font-size:2.4rem;margin-bottom:8px}
.muted{color:var(--muted)}
.small{font-size:.85rem}
.file-info{border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-top:16px;background:#f8fafc}
.file-name{font-weight:700;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.file-sub{font-size:.88rem}
.options{display:flex;flex-wrap:wrap;gap:20px 48px;margin:22px 0 6px}
.opt-group{border:none}
.opt-group legend{font-weight:600;margin-bottom:8px;padding:0}
.radio{display:block;margin:6px 0;cursor:pointer}
.actions{display:flex;gap:12px;flex-wrap:wrap;margin:16px 0 8px}
.btn{border:none;border-radius:10px;padding:12px 22px;font-size:.95rem;font-weight:600;cursor:pointer;text-decoration:none;display:inline-block;text-align:center}
.btn:disabled{opacity:.45;cursor:not-allowed}
.btn-primary{background:var(--blue);color:#fff}
.btn-primary:hover:not(:disabled){background:#1e40af}
.btn-ghost{background:#eef2ff;color:var(--blue)}
.btn-ghost:hover:not(:disabled){background:#e0e9ff}
.btn-sm{padding:8px 14px;font-size:.85rem;border-radius:8px}
.engine-note{background:#f1f5f9;border-radius:10px;padding:10px 14px;margin-top:12px}
.progress-wrap{margin-top:18px}
.progress{height:14px;background:#e2e8f0;border-radius:999px;overflow:hidden}
.progress > i{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--blue),var(--purple));transition:width .25s}
.progress-wrap p{margin-top:8px}
.result{margin-top:18px;border:1px solid #bbf7d0;background:#f0fdf4;border-radius:12px;padding:18px}
.result-head{font-size:1.05rem;margin-bottom:6px}
.result p{margin-bottom:12px}
.error-card{margin-top:18px;border:1px solid #fecaca;background:#fef2f2;border-radius:12px;padding:18px}
.error-card p{margin-bottom:8px}
.target-row{display:flex;flex-wrap:wrap;gap:16px;align-items:flex-end;margin:18px 0 6px}
.field label{font-weight:600;display:block;margin-bottom:6px}
.field input[type=number]{font-size:1.1rem;padding:10px 12px;border:2px solid var(--line);border-radius:10px;width:160px}
.field input[type=number]:focus{outline:none;border-color:var(--blue)}
.presets{display:flex;gap:8px;flex-wrap:wrap}
.chip{border:2px solid var(--line);background:#fff;border-radius:999px;padding:8px 16px;font-weight:600;cursor:pointer;color:var(--ink);font-size:.9rem}
.chip:hover{border-color:var(--blue);color:var(--blue)}
.chip.active{background:var(--blue);border-color:var(--blue);color:#fff}
.stat-row{display:flex;flex-wrap:wrap;gap:12px 28px;margin:14px 0}
.stat{background:#f8fafc;border:1px solid var(--line);border-radius:10px;padding:10px 16px}
.stat .k{font-size:.78rem;color:var(--muted);text-transform:uppercase;letter-spacing:.04em}
.stat .v{font-size:1.15rem;font-weight:800}
.saved{color:var(--green)}
.faq h2{margin-bottom:14px}
.faq details{border:1px solid var(--line);border-radius:10px;padding:14px 16px;margin:10px 0;background:#fff}
.faq summary{font-weight:600;cursor:pointer}
.faq p{margin-top:8px;color:var(--muted)}
.site-footer{text-align:center;padding:28px 0 40px;color:#94a3b8;font-size:.85rem}
.toast{position:fixed;left:50%;bottom:24px;transform:translateX(-50%) translateY(20px);background:#1e293b;color:#fff;padding:12px 20px;border-radius:10px;opacity:0;pointer-events:none;transition:opacity .2s,transform .2s;max-width:90vw;text-align:center;z-index:50}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
@media (max-width:640px){
  .hero h1{font-size:1.5rem}
  .card{padding:20px 16px}
}