*{box-sizing:border-box}
body{font-family:system-ui,-apple-system,Segoe UI,Roboto,'Helvetica Neue',Arial; margin:0; padding:0; display:flex; flex-direction:column; min-height:100vh}
header{background:#0b5fff;color:white;padding:12px 16px;display:flex;align-items:center;justify-content:space-between}
header h1{font-size:16px;margin:0}
nav{display:flex;gap:8px;align-items:center}
button, select{padding:8px 10px;border-radius:8px;border:0;background:rgba(255,255,255,0.12);color:white}
main{display:flex;flex:1;gap:12px;padding:12px;flex-wrap:wrap}
.editor, .preview{flex:1 1 480px;min-width:300px;display:flex;flex-direction:column;gap:8px}
#code{height:50vh;width:100%;padding:8px;font-family:ui-monospace, SFMono-Regular, Menlo, Monaco, 'Roboto Mono', monospace;font-size:14px;resize:vertical}
iframe#output{flex:1;border:1px solid #ddd;border-radius:6px;background:white}
.controls{display:flex;gap:8px;align-items:center}
footer{padding:8px 12px;background:#f6f7fb;color:#333}
@media (max-width:800px){main{flex-direction:column}header{flex-direction:column;align-items:flex-start}nav{flex-wrap:wrap}}