.confetti {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none; /* クリックを通す */
  z-index: 9999;        /* 最前面に表示 */
  overflow: hidden;
}
.confetti canvas {
  height: 100%;
  width: 100%;
  position: absolute;
  background: transparent;
}