:root{
  --bg:#f6f8fb;
  --surface:#ffffff;
  --text:#0f172a;
  --muted:#475569;
  --border:#e2e8f0;
  --accent:#2563eb;
  --accent-2:#38bdf8;
  --shadow: 0 10px 24px rgba(2,6,23,.08);
}
*{box-sizing:border-box}
html,body{height:100%}
body{margin:0;font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Ubuntu,'Helvetica Neue',Arial;background:var(--bg);color:var(--text);display:flex;flex-direction:column}
.app-header,.app-footer{padding:12px 16px;display:flex;align-items:center;justify-content:space-between;background:#fff;border-bottom:1px solid var(--border)}
.app-footer{border-top:1px solid var(--border);border-bottom:none;justify-content:center;font-size:.9rem;opacity:.9}
.brand{display:flex;align-items:center;gap:10px}
.logo{height:36px;width:36px;border-radius:10px;display:grid;place-items:center;background:linear-gradient(145deg,var(--accent),var(--accent-2));color:white;font-weight:900;box-shadow:var(--shadow)}
h1{font-size:1.1rem;margin:0}
main{padding:18px;max-width:1100px;margin:0 auto;flex:1;width:100%}
.card{background:var(--surface);border:1px solid var(--border);border-radius:14px;padding:16px;margin:10px 0;box-shadow:var(--shadow)}
.tabs{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-bottom:14px}
.tab{background:transparent;border:1.5px solid var(--border);border-radius:12px;color:var(--muted);padding:12px 10px;font-weight:700}
.tab.active{background:linear-gradient(145deg,var(--accent),var(--accent-2));color:#fff;border-color:transparent;box-shadow:var(--shadow)}
.panel{display:none}
.panel.active{display:block;animation:fade .18s ease-out}
@keyframes fade{from{opacity:.7;transform:translateY(2px)}to{opacity:1;transform:none}}
.grid{display:grid;gap:12px;margin:10px 0}
.grid.two{grid-template-columns:repeat(2,1fr)}
@media(min-width:640px){.grid{grid-template-columns:repeat(2,1fr)}}
label{display:flex;flex-direction:column;gap:8px;font-size:.97rem;color:#1f2937}
input,select,button{padding:14px 12px;border-radius:12px;border:1px solid #cbd5e1;background:#fff;color:var(--text);font-size:1.02rem;transition:all .15s}
input:focus,select:focus,button:focus{outline:2px solid var(--accent);outline-offset:1px}
button{cursor:pointer}
button.primary{background:linear-gradient(145deg,var(--accent),var(--accent-2));border:0;color:#fff;font-weight:800}
button.ghost{background:#f8fafc;border-color:#e2e8f0;color:#0f172a}
.result{display:block;margin-top:12px;padding:16px;border-radius:12px;background:#f8fafc;border:1px dashed #cbd5e1;font-size:1.05rem;line-height:1.35}
.result-row{display:grid;grid-template-columns:1fr auto;gap:10px;align-items:stretch}
.copy-btn{height:100%; padding:0 14px; border-radius:12px}
.row{display:flex;align-items:center;gap:8px}
.hint{font-size:.9rem;color:#475569;margin-top:6px}
/* Stretch/mobile tweaks */
input,select{width:100%; -webkit-appearance:none; appearance:textfield}
input[type=number]::-webkit-outer-spin-button,
input[type=number]::-webkit-inner-spin-button{ -webkit-appearance: none; margin: 0; }
@media(max-width:640px){
  .tabs{grid-template-columns:1fr}
  .grid.two{grid-template-columns:1fr}
  main{padding:14px}
}
/* v3: Match heights for result and Copy button */
.result{display:flex; align-items:center; padding:14px 16px; min-height:48px}
.copy-btn{display:flex; align-items:center; justify-content:center; min-height:48px; height:100%; padding:0 16px; font-weight:700}