:root{
  --bg:#0b1020;
  --panel:#131a2e;
  --panel2:#0f1526;
  --ink:#e6edf7;
  --muted:#94a3b8;
  --accent:#22d3ee;
  --accent2:#6366f1;
  --line:#26314d;
  --ok:#34d399;
  --radius:14px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
  background:
    radial-gradient(1200px 600px at 80% -10%, #14203c 0%, transparent 60%),
    radial-gradient(900px 500px at 10% 0%, #0e1a33 0%, transparent 55%),
    var(--bg);
  color:var(--ink);
  line-height:1.5;
}
.container{max-width:1120px;margin:0 auto;padding:0 20px}

/* header */
header{padding-top:28px}
.header-inner{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:14px}
.logo{width:64px;height:64px}
.brand h1{margin:0;font-size:1.5rem;letter-spacing:.3px}
.tagline{margin:2px 0 0;color:var(--muted);font-size:.85rem}
nav{display:flex;gap:8px;flex-wrap:wrap}
nav a{
  color:var(--muted);text-decoration:none;font-size:.9rem;
  padding:8px 12px;border-radius:10px;border:1px solid transparent;
  transition:.15s;
}
nav a:hover{color:var(--accent);border-color:var(--line);background:rgba(34,211,238,.06)}
.hero-wave{width:100%;max-width:1120px;margin:8px auto 0;display:block;opacity:.8}

/* sections */
section{padding:44px 20px 10px}
section h2{
  font-size:1.35rem;margin:0 0 18px;
  padding-bottom:10px;border-bottom:1px solid var(--line);
}
.section-img{width:100%;max-width:520px;border-radius:var(--radius);margin:0 0 14px;
  border:1px solid var(--line);background:var(--panel2)}
.section-note{color:var(--muted);max-width:760px;margin:0 0 24px;font-size:.95rem}
.section-note code{background:#0c1220;padding:1px 6px;border-radius:6px;color:var(--accent);font-size:.85em}

/* calc grid */
.calc-grid{display:grid;gap:18px;grid-template-columns:repeat(auto-fit,minmax(300px,1fr))}
.calc-grid.two{grid-template-columns:repeat(auto-fit,minmax(300px,1fr))}
.calc-grid.one{grid-template-columns:minmax(300px,420px)}

.calc-card{
  background:linear-gradient(180deg,var(--panel) 0%,var(--panel2) 100%);
  border:1px solid var(--line);border-radius:var(--radius);
  padding:18px 18px 20px;
  box-shadow:0 8px 24px rgba(0,0,0,.25);
}
.calc-card h3{margin:0 0 14px;font-size:1.05rem;display:flex;align-items:center;gap:8px}
.calc-card h3::before{content:"";width:8px;height:8px;border-radius:50%;
  background:linear-gradient(135deg,var(--accent),var(--accent2));display:inline-block}

label{display:block;font-size:.85rem;color:var(--muted);margin-bottom:12px}
label input[type=number]{
  width:100%;margin-top:6px;padding:9px 10px;border-radius:9px;
  border:1px solid var(--line);background:#0c1220;color:var(--ink);
  font-size:.95rem;outline:none;
}
label input[type=number]:focus{border-color:var(--accent)}
.row{display:flex;gap:8px;margin-top:6px}
.row input{flex:1;margin-top:0}
.row select{
  background:#0c1220;color:var(--ink);border:1px solid var(--line);
  border-radius:9px;padding:0 10px;min-width:64px;outline:none;
}
.row select:focus{border-color:var(--accent)}

button[type=submit]{
  width:100%;margin-top:4px;padding:11px 0;border:none;border-radius:10px;
  font-size:.95rem;font-weight:600;color:#04121a;cursor:pointer;
  background:linear-gradient(135deg,var(--accent),var(--accent2));
  transition:filter .15s,transform .05s;
}
button[type=submit]:hover{filter:brightness(1.1)}
button[type=submit]:active{transform:translateY(1px)}

.result{
  margin-top:16px;padding:12px 14px;border-radius:10px;
  background:#0a0f1d;border:1px solid var(--line);
  font-size:1.05rem;font-weight:600;color:var(--ok);min-height:48px;
}
.result span{color:var(--accent)}
.hint{color:var(--muted);font-size:.78rem;margin:12px 0 0}
.hint sub{font-size:.7em}

footer{padding:36px 20px 40px;text-align:center;color:var(--muted);font-size:.85rem;
  border-top:1px solid var(--line);margin-top:40px}

@media (max-width:560px){
  .brand h1{font-size:1.2rem}
  .logo{width:48px;height:48px}
}