:root {
  --bg: #f6f8fb;
  --panel: #ffffff;
  --text: #0b1220;
  --muted: #6b7280;
  --primary: #2563eb;
  --primary-hover: #1e4fc4;
  --border: #e5e7eb;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg);
  color: var(--text);
}

/* Dark mode */
body.dark {
  --bg: #0d1117;
  --panel: #0f172a;
  --text: #e5e7eb;
  --muted: #9aa4b2;
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --border: #1f2937;
}

.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 20px; border-bottom: 1px solid var(--border);
  background: var(--panel); position: sticky; top: 0; z-index: 50;
}
.brand { display: flex; align-items: center; gap: 10px; font-size: 16px; }
.brand .dot { width: 10px; height: 10px; border-radius: 50%; background: var(--primary); display: inline-block; }

.container {
  max-width: 1100px; margin: 30px auto; padding: 0 16px;
  display: grid; grid-template-columns: 1fr; gap: 20px;
}
@media (min-width: 960px) {
  .container { grid-template-columns: 520px 1fr; align-items: start; }
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 22px;
  box-shadow: 0 6px 20px rgba(0,0,0,0.05);
}

h1 { margin: 0 0 8px 0; font-size: 22px; }
.muted { color: var(--muted); margin: 0 0 14px 0; }

.grid {
  display: grid; gap: 12px; grid-template-columns: 1fr 1fr;
}
.grid .field:nth-child(1) { grid-column: span 2; }
@media (max-width: 640px) {
  .grid { grid-template-columns: 1fr; }
  .grid .field:nth-child(1) { grid-column: span 1; }
}

.field { display: grid; gap: 6px; }
.field span { font-size: 13px; color: var(--muted); }
input, select, textarea {
  width: 100%; padding: 12px 12px;
  border: 1px solid var(--border); border-radius: 10px;
  background: transparent; color: var(--text); font-size: 15px;
}
input:focus, select:focus, textarea:focus { outline: 2px solid var(--primary); outline-offset: 2px; }

.actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
button {
  border: 0; cursor: pointer;
  padding: 12px 16px; border-radius: 12px;
  background: var(--primary); color: #fff; font-weight: 600;
}
button:hover { background: var(--primary-hover); }
button.secondary {
  background: transparent; color: var(--primary);
  border: 1px solid var(--primary);
}
button.secondary:hover { background: rgba(37,99,235,0.08); }
button.ghost {
  background: transparent; color: var(--muted);
  border: 1px solid var(--border);
}
button.ghost:hover { color: var(--text); }

.hint { margin-top: 10px; }
.codeblock {
  display: block; margin-top: 10px; padding: 12px;
  white-space: pre; background: #0d1117; color: #e5e7eb;
  border-radius: 10px; overflow: auto; border: 1px solid #111827;
}
body.dark .codeblock { background: #0b0f1a; border-color: #0b1220; }

.preview {
  position: relative;
  background: var(--panel);
  border: 1px solid var(--border); border-radius: 14px;
  padding: 16px; min-height: 380px;
  display: grid; place-items: center;
}
.placeholder { text-align: center; color: var(--muted); }
.spinner {
  width: 26px; height: 26px; border: 3px solid var(--border);
  border-top-color: var(--primary); border-radius: 50%;
  margin: 8px auto 10px; animation: spin 0.9s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

#iframeContainer > iframe {
  border: none; border-radius: 14px;
  width: 100%; max-width: 420px; height: 745px;
  box-shadow: 0 10px 30px rgba(0,0,0,.12);
}

.foot { text-align: center; color: var(--muted); padding: 24px 0 40px; }