:root{
  --bg:#ffffff;
  --card:#f8fafc;
  --accent:#1f6feb;
  --muted:#4b5563;
  --danger:#ef4444;
  --surface-border:#e6eef8;
  --control-bg:#ffffff;
}

/* Dark theme variables */
:root[data-theme="dark"]{
  --bg:#071028;
  --card:#071a2b;
  --accent:#60a5fa;
  --muted:#9fb0c6;
  --danger:#fb7185;
  --surface-border:#123248;
  --control-bg:#0b2030;
}

*{box-sizing:border-box}
html,body{height:100%;margin:0;font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial}
body{background:var(--bg);display:flex;align-items:center;justify-content:center;padding:28px;color:var(--text);font-size:18px;line-height:1.5}
.container{width:100%;max-width:960px;background:var(--card);padding:24px;border-radius:12px;box-shadow:0 6px 20px rgba(16,24,40,0.06);border:1px solid var(--surface-border)}
h1{margin:0 0 12px 0;font-size:28px;font-weight:600}
.calculator .row{display:flex;flex-direction:column;margin-bottom:14px}
.calculator label{font-size:15px;color:var(--muted);margin-bottom:8px}
.calculator input, .calculator select{padding:12px;border-radius:8px;border:1px solid var(--surface-border);font-size:16px;background:var(--control-bg);color:var(--text)}
.actions{display:flex;gap:10px}
button{background:var(--accent);color:var(--accent-foreground, #fff);padding:12px 16px;border-radius:10px;border:none;font-weight:700;cursor:pointer;font-size:16px}
button.secondary{background:#eef2ff;color:var(--accent)}
#theme-toggle{background:transparent;border:0;font-size:18px;cursor:pointer;padding:6px;margin-left:8px}
.result{background:var(--card);border-radius:8px;padding:12px;border:1px solid var(--surface-border)}
#result{font-size:20px;color:var(--muted);font-weight:600}
footer{margin-top:18px;font-size:14px;color:var(--muted)}
footer .site-credit{margin-top:8px;font-size:13px;color:var(--muted);text-align:right}
@media (max-width:480px){.container{padding:18px}}

button:focus, input:focus, select:focus{outline:3px solid rgba(31,111,235,0.16);outline-offset:2px}
