:root{
  --blue-700:#005fa3;
  --blue-600:#0077cc;
  --blue-500:#0096e6;
  --muted:#6b7280;
  --card:#ffffff;
  --glass: rgba(0,0,0,0.04);
  --radius:12px;
  --max-width:1100px;
  --bg:#f4f8fb;
}

/* Dark theme variables (will be toggled via data-theme attribute) */
:root[data-theme="dark"]{
  --blue-700:#7fb6ff;
  --blue-600:#66a3e0;
  --blue-500:#4d90c3;
  --muted:#b7c2d1;
  --card:#0f1724;
  --glass: rgba(255,255,255,0.04);
  --bg:#071027;
  color-scheme: dark;
}

*{box-sizing:border-box}
body{
  margin:0;
  font-family: Inter, system-ui, -apple-system, "Helvetica Neue", Arial;
  background: linear-gradient(180deg,var(--bg) 0%, #ffffff 100%);
  color:#0f172a;
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
  line-height:1.45;
}

.container{max-width:var(--max-width);margin:20px auto;padding:0 18px}

/* header */
.site-header{background:var(--blue-600);color:white;padding:14px 0;box-shadow:0 6px 20px rgba(0,0,0,0.08)}
.header-inner{display:flex;align-items:center;justify-content:space-between;gap:20px}
.brand{display:flex;gap:12px;align-items:center}
.logo{width:48px;height:48px;border-radius:8px;box-shadow:0 3px 10px rgba(0,0,0,0.12)}
.brand h1{margin:0;font-size:18px;letter-spacing:0.2px}
.brand .subtitle{margin:0;font-size:13px;opacity:0.95}

/* main panel */
.panel{background:var(--card);border-radius:var(--radius);padding:20px;margin-top:20px;box-shadow:0 6px 30px rgba(2,6,23,0.06)}
.grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-top:8px}
.card{background:linear-gradient(180deg,#fff,#fbfdff);padding:14px;border-radius:10px;border:1px solid var(--glass)}
.card h3{margin:0 0 8px 0;font-size:15px}
label{font-size:13px;color:var(--muted);margin-top:8px;display:block}
select,input[type="text"],.checkboxes input{padding:8px;border-radius:8px;border:1px solid #e6eef8;background:#fff;width:100%}
.checkboxes{display:flex;flex-direction:column;gap:6px;margin-top:8px}
.actions{display:flex;gap:12px;margin-top:18px;flex-wrap:wrap}
button{background:var(--blue-600);color:white;border:none;padding:12px 16px;border-radius:10px;cursor:pointer;font-weight:600}
button.secondary{background:transparent;color:var(--blue-700);border:1px solid rgba(0,0,0,0.06)}
.small-btn{background:transparent;color:white;border:1px solid rgba(255,255,255,0.12);padding:6px 8px;border-radius:8px;cursor:pointer}
.result{margin-top:18px;padding:14px;border-radius:10px;background:linear-gradient(180deg,#f0f8ff,#eef8ff);border:1px solid rgba(0,111,180,0.06)}
.result strong{color:var(--blue-700);font-size:20px}

/* info and notes */
.info{margin-top:8px;color:var(--muted);font-size:14px}
.notes ul{margin:8px 0 0 18px;color:var(--muted)}
.small{font-size:13px}
.muted{color:var(--muted)}

/* footer */
.site-footer{margin-top:20px;padding:12px 0;color:var(--muted)}
.footer-inner{display:flex;justify-content:space-between;align-items:center;gap:12px}

/* responsive */
@media (max-width:980px){
  .grid{grid-template-columns:1fr; }
  .header-inner{flex-direction:column;align-items:flex-start;gap:8px}
  .brand h1{font-size:16px}
}

/* small tweaks for dark mode */
:root[data-theme="dark"] .panel{box-shadow:none}
:root[data-theme="dark"] .card{background:linear-gradient(180deg,#0b1624,#08121a);border:1px solid rgba(255,255,255,0.03)}
:root[data-theme="dark"] .result{background:linear-gradient(180deg,#081827,#07202b);border:1px solid rgba(255,255,255,0.03)}
:root[data-theme="dark"] body{color:var(--muted)}