/* ===== Three.js 背景层 ===== */
#canvas-container {
  position: fixed; top: 0; left: 0; width: 100%; height: 100%; z-index: 0; pointer-events: none;
}
.background-overlay {
  position: fixed; top: 0; left: 0; width: 100%; height: 100%;
  background-image:
    linear-gradient(var(--grid-color) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
  background-size: 80px 80px; z-index: 1; pointer-events: none;
}

/* ===== 导航 & 内容层级 ===== */
main, #site-footer { position: relative; z-index: 10; }
main.page-main { z-index: 10; background: transparent; padding-top: 0; min-height: 0; }