let targetOpacity = show ? (elapsedTime / duration) : 1-(elapsedTime / duration);
this.container.style.opacity = targetOpacity;
if (elapsedTime > duration) {
let targetOpacity = show ? (elapsedTime / duration) : 1-(elapsedTime / duration);
this.container.style.opacity = targetOpacity;
if (elapsedTime > duration) {