:root {
  --bg: #0f172a;
  --panel: #111827;
  --muted: #94a3b8;
  --text: #e5e7eb;
  --primary: #4f46e5;
  --primary-700: #4338ca;
  --accent: #10b981;
  --danger: #ef4444;
  --border: #1f2937;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: 'Inter', system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: radial-gradient(1200px 600px at 10% -10%, #312e81 0, transparent 40%),
              radial-gradient(1200px 600px at 110% 10%, #0f766e 0, transparent 30%),
              var(--bg);
  color: var(--text);
}

.app { max-width: 900px; margin: 24px auto; padding: 16px; }

.header { display: flex; flex-direction: column; gap: 12px; margin-bottom: 16px; }
.header h1 { margin: 0; font-size: 22px; font-weight: 700; }
.project-attribution {
  margin-top: 8px;
  color: rgba(255, 255, 255, 0.75);
  font-size: 0.95rem;
  font-weight: 500;
  letter-spacing: 0.2px;
  text-align: left;
}
.project-attribution a {
  color: inherit;
  text-decoration: none;
}
.project-attribution a:hover {
  color: var(--text);
  text-decoration: underline;
}
.clock { color: var(--muted); font-size: 14px; }

.mode-switch { display: flex; flex-wrap: wrap; gap: 8px; }
.mode-btn {
  background: #0b1220;
  border: 1px solid var(--border);
  color: var(--text);
  padding: 8px 12px;
  border-radius: 10px;
  cursor: pointer;
}
.mode-btn[aria-selected="true"] { background: var(--primary); border-color: var(--primary); }
.mode-btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.panes { background: rgba(17, 24, 39, 0.6); border: 1px solid var(--border); border-radius: 16px; padding: 16px; box-shadow: 0 20px 60px rgba(0,0,0,0.35); }

.pane.hidden { display: none; }

.calc { display: flex; flex-direction: column; gap: 12px; }
.display {
  width: 100%;
  height: 56px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: #0b1220;
  color: var(--text);
  padding: 8px 12px;
  font-size: 22px;
}

.grid { display: grid; gap: 8px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
.grid-6 { grid-template-columns: repeat(6, 1fr); }
.gap { gap: 12px; }

.key {
  background: linear-gradient(180deg, #0f1627, #0b1220);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 14px 10px;
  border-radius: 12px;
  font-size: 16px;
  cursor: pointer;
}
.key-op { color: #c7d2fe; }
.key-fn { color: #fca5a5; }
.key-eq { background: linear-gradient(180deg, var(--primary), var(--primary-700)); border-color: var(--primary-700); }
.key-span-2 { grid-column: span 2; }
.key:active { transform: translateY(1px); }

.form { display: flex; flex-direction: column; gap: 12px; }
.row { display: flex; gap: 12px; align-items: center; }
.row label { width: 180px; color: var(--muted); }
.row input, .row select {
  flex: 1;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: #0b1220;
  color: var(--text);
  padding: 10px 12px;
}
.btn {
  background: var(--accent);
  color: #052e2b;
  border: none;
  padding: 10px 14px;
  border-radius: 10px;
  cursor: pointer;
}
.btn-secondary {
  background: #0b1220;
  color: var(--text);
  border: 1px solid var(--border);
}

.result { padding: 12px; background: #0b1220; border: 1px solid var(--border); border-radius: 10px; min-height: 48px; display: flex; align-items: center; }

@media (max-width: 720px) {
  .row { flex-direction: column; align-items: stretch; }
  .row label { width: auto; }
  .project-attribution { text-align: center; }
}