html, body {
  height: 100%;
  margin: 0;
}

body {
  background: radial-gradient(1200px 600px at 50% 30%, #0f172a, #020617);
  color: #e2e8f0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
}

canvas {
  display: block;
}

/* Layout */
#app {
  height: 100vh;
  display: grid;
  grid-template-columns: 280px 1fr;
}

#sidebar {
  box-sizing: border-box;
  padding: 16px;
  background: rgba(2, 6, 23, 0.7);
  border-right: 1px solid rgba(148, 163, 184, 0.15);
  backdrop-filter: blur(6px);
  height: 100vh; /* own scroll */
  overflow-y: auto;
}

#sidebar h1 {
  margin: 0 0 12px 0;
  font-size: 16px;
  font-weight: 600;
  color: #f1f5f9;
}

.control {
  display: grid;
  gap: 8px;
  margin-bottom: 16px;
}

label {
  font-size: 12px;
  color: #94a3b8;
}

input[type="color"] {
  width: 100%;
  height: 36px;
  padding: 0;
  border: 1px solid rgba(148, 163, 184, 0.25);
  border-radius: 6px;
  background: #0b1220;
}

#viewport {
  position: relative;
  height: 100vh; /* ensure canvas fits full viewport height */
  overflow: hidden;
  overscroll-behavior: contain; /* keep trackpads from rubberbanding page */
}

/* Loading overlay */
#loadingOverlay {
  position: fixed;
  inset: 0;
  display: none; /* shown while loading */
  align-items: center;
  justify-content: center;
  background: rgba(2, 6, 23, 0.85);
  z-index: 1000;
}

#loadingOverlay .loader-box {
  display: grid;
  gap: 12px;
  place-items: center;
  padding: 16px 24px;
  border: 1px solid rgba(148,163,184,0.25);
  background: #0b1220;
  border-radius: 8px;
  color: #e2e8f0;
  font-size: 14px;
}

.spinner {
  width: 28px;
  height: 28px;
  border-radius: 9999px;
  border: 3px solid rgba(148,163,184,0.25);
  border-top-color: #38bdf8;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

button {
  appearance: none;
  border: 1px solid rgba(148, 163, 184, 0.25);
  background: #0b1220;
  color: #e2e8f0;
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 13px;
  cursor: pointer;
}

button:hover {
  background: #111827;
}

hr {
  border: none;
  border-top: 1px solid rgba(148, 163, 184, 0.15);
  margin: 16px 0;
}

h2 {
  margin: 0 0 8px 0;
  font-size: 13px;
  font-weight: 600;
  color: #e2e8f0;
}

.two-cols {
  grid-template-columns: 1fr 1fr;
  display: grid;
  gap: 12px;
}

.row {
  display: grid;
  grid-template-columns: auto 1fr auto auto;
  gap: 8px;
  align-items: center;
}

input[type="range"] {
  width: 100%;
}

select {
  width: 100%;
  padding: 6px 8px;
  border: 1px solid rgba(148, 163, 184, 0.25);
  border-radius: 6px;
  background: #0b1220;
  color: #e2e8f0;
}

/* Removed region highlight styles */

/* Responsive: stack sidebar on top for mobile */
@media (max-width: 768px) {
  #app {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 3fr; /* 1/4 controls, 3/4 canvas */
  }
  #sidebar {
    height: auto;
    max-height: none;
    border-right: none;
    border-bottom: 1px solid rgba(148, 163, 184, 0.15);
    overflow-y: auto;
  }
  #viewport {
    height: auto; /* grid row controls height (2/3) */
    min-height: 0;
  }
}