.top{background:#222;color:white;padding:15px;font-size:22px}
body{margin:0;font-family:Arial;background:#eee}
.layout{display:grid;grid-template-columns:250px 1fr 250px;gap:10px;padding:10px}
.panel,.viewer{background:white;padding:10px;border-radius:8px}
#svg{width:100%;height:350px;border:1px solid #999}
#canvas3d{height:400px;background:#111}
button{padding:10px;width:100%}