*{margin:0}body{margin:0;overflow:hidden;position:relative}#control-panel{position:absolute;top:10px;right:10px;z-index:10;background:#ffffffe6;padding:6px;border-radius:4px;display:flex;flex-direction:column;gap:6px}#control-panel button{padding:6px 12px;border:2px solid #ccc;background:#fff;cursor:pointer;font-weight:700;transition:border .2s,background .2s}#control-panel button.active{border:3px solid #000;background:#eee}#selection-rect{position:absolute;border:1px dashed #888;background:#c8c8ff33;pointer-events:none;display:none;z-index:1000}