:root {
  --bg: #f4f8ff;
  --card: rgba(255,255,255,.88);
  --text: #0f172a;
  --muted: #64748b;
  --border: rgba(15,23,42,.12);
  --blue: #0b74de;
  --blue2: #38bdf8;
  --shadow: 0 18px 50px rgba(2, 8, 23, .12);
}
:root[data-theme="dark"] {
  --bg: #07111f;
  --card: rgba(15,23,42,.86);
  --text: #e5eefc;
  --muted: #94a3b8;
  --border: rgba(148,163,184,.18);
  --blue: #1d8cf8;
  --blue2: #67e8f9;
  --shadow: 0 20px 60px rgba(0,0,0,.35);
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, Segoe UI, Arial, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 10% 5%, rgba(29,140,248,.25), transparent 28%),
    radial-gradient(circle at 80% 10%, rgba(103,232,249,.16), transparent 30%),
    var(--bg);
  min-height: 100vh;
}
.topbar, .app-shell { max-width: 1180px; margin: 0 auto; }
.topbar { display:flex; justify-content:space-between; align-items:center; padding: 26px 20px; }
.brand { display:flex; align-items:center; gap:14px; }
.logo-mark {
  width: 52px; height: 52px; display:grid; place-items:center;
  border-radius: 16px; font-weight: 900; letter-spacing:-1px;
  background: linear-gradient(135deg, var(--blue), var(--blue2));
  color: white; box-shadow: var(--shadow);
}
h1,h2,h3,p { margin:0; }
.brand h1 { font-size: 28px; letter-spacing: -.04em; }
.brand p, .hero-card p, .preview-head p, .upload-card p { color: var(--muted); }
.top-actions { display:flex; gap:10px; }
.ghost, .link {
  border:1px solid var(--border); background:var(--card); color:var(--text);
  padding:10px 14px; border-radius:14px; text-decoration:none; cursor:pointer;
}
.app-shell { padding: 0 20px 42px; }
.hero-card, .upload-card, .panel, .preview-panel, .login-card {
  background: var(--card); border: 1px solid var(--border); border-radius: 26px;
  box-shadow: var(--shadow); backdrop-filter: blur(14px);
}
.hero-card { padding: 26px; display:flex; justify-content:space-between; align-items:center; gap:16px; }
.hero-card h2 { font-size: 28px; margin-bottom: 6px; }
.badge { color:white; background:linear-gradient(135deg, var(--blue), var(--blue2)); border-radius:999px; padding:10px 14px; font-weight:700; white-space:nowrap;}
.upload-card { margin-top:18px; padding:44px; text-align:center; border-style:dashed; cursor:pointer; }
.upload-card.drag { transform: scale(1.01); border-color: var(--blue); }
.upload-icon { font-size: 62px; color: var(--blue); line-height:1; }
.upload-card h3 { font-size: 24px; margin: 10px 0 6px; }
.grid { display:grid; grid-template-columns: 1.1fr .9fr; gap:18px; margin-top:18px; }
.panel { padding:24px; }
.panel h3 { margin-bottom:18px; }
label { display:block; color:var(--muted); margin:14px 0 8px; font-size:14px; }
select,input {
  width:100%; padding:13px 14px; border-radius:14px; border:1px solid var(--border);
  background: rgba(255,255,255,.08); color: var(--text); outline:none;
}
.check { display:flex; gap:10px; align-items:center; color:var(--text); }
.check input { width:auto; }
button#convertBtn, .login-card button {
  margin-top:18px; width:100%; border:none; border-radius:16px; padding:15px 18px;
  background:linear-gradient(135deg, var(--blue), var(--blue2)); color:white; font-weight:800;
  cursor:pointer;
}
button:disabled { opacity:.5; cursor:not-allowed; }
.file-info { padding:16px; border-radius:18px; border:1px solid var(--border); color:var(--muted); }
.tips { margin-top:18px; padding:16px; border-radius:18px; background:rgba(29,140,248,.12); color:var(--muted); }
.tips strong { color:var(--text); }
.preview-panel { margin-top:18px; padding:24px; overflow:hidden; }
.preview-head { display:flex; justify-content:space-between; margin-bottom:16px; }
.preview-table { overflow:auto; max-height:420px; border:1px solid var(--border); border-radius:18px; }
.preview-table table { width:100%; border-collapse:collapse; min-width:760px; }
.preview-table td { border-bottom:1px solid var(--border); border-right:1px solid var(--border); padding:9px 11px; white-space:nowrap; font-size:13px; }
.preview-table tr.sf-head td { background:rgba(29,140,248,.16); font-weight:700; }
.error, .alert { padding:14px; border-radius:14px; background:rgba(239,68,68,.14); color:#ef4444; }
.login-body { display:grid; place-items:center; padding:24px; }
.login-card { width:min(440px, 100%); padding:30px; }
.login-card .brand { margin-bottom:24px; }
.login-card form label { margin-top:14px; }
@media (max-width: 820px) {
  .topbar, .hero-card { flex-direction:column; align-items:flex-start; }
  .grid { grid-template-columns:1fr; }
  .badge { white-space:normal; }
}