:root {
  --gap: 10px;
  --panel-bg: #121212;
  --panel-fg: #e0e0e0;
  --accent: #1e90ff;
  --editor-bg: #1b1b1b;
  --tab-bg: #1f1f1f;
  --tab-active1: #3a6ff5;
  --tab-active2: #1454d0;
  --border-light: rgba(255,255,255,0.1);
  --border-soft: rgba(255,255,255,0.05);
  --preview-bg: #fefefe;
  --preview-header-bg: #222222;
  --preview-header-fg: #f0f0f0;
  --preview-title-fg: #fefefe;
}
*{box-sizing:border-box}
html,body{height:100%;margin:0;font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,"Helvetica Neue",Arial}
.app{display:grid;grid-template-columns:500px 1fr;gap:var(--gap);height:100vh;padding:var(--gap);background:var(--panel-bg);color:var(--panel-fg)}
.left{display:flex;flex-direction:column;gap:var(--gap)}
.tabs{display:flex;gap:4px}
.tab{background:var(--tab-bg);padding:6px 10px;border-radius:6px;cursor:pointer;border:1px solid transparent;font-size:13px;user-select:none}
.tab.active{background:linear-gradient(180deg,var(--tab-active1),var(--tab-active2));border-color:var(--border-light);font-weight:bold}
.editor{flex:1;display:flex;flex-direction:column;border-radius:6px;overflow:hidden;border:1px solid var(--border-soft)}
textarea{flex:1;width:100%;padding:10px;background:var(--editor-bg);color:var(--panel-fg);border:none;resize:none;font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,monospace;font-size:13px;line-height:1.45}
.controls{display:flex;gap:6px;padding:6px;background:var(--tab-bg);border-top:1px solid var(--border-soft)}
button{background:transparent;border:1px solid var(--border-light);color:var(--panel-fg);padding:6px 10px;border-radius:6px;cursor:pointer;font-size:13px}
.right{background:var(--preview-bg);border-radius:6px;overflow:hidden;display:flex;flex-direction:column}
.previewTop{display:flex;align-items:center;justify-content:space-between;padding:6px 10px;background:var(--preview-header-bg);color:var(--preview-header-fg);font-weight:600}
.previewTitle{display:flex;align-items:center;gap:6px}
.previewTitle img{width:16px;height:16px}
iframe{flex:1;border:0}
.small{font-size:12px;opacity:0.8}
.hint{font-size:12px;color:#9fb3ff}
@media (max-width:900px){.app{grid-template-columns:1fr;grid-auto-rows:1fr}}