html, body, main { background: #000; }
main { isolation: isolate; }
#background { position: absolute; inset: 0; z-index: 0; pointer-events: none; }
#background canvas { cursor: default; }
#installCanvas { position: absolute; inset: 0; z-index: 1; background: transparent; }

/* 防止移动端连续轻触触发双击缩放，保留正常点按。 */
#installCanvas { touch-action: manipulation; }