ease: "power1.in"
// start slow and end faster, like a heavy object falling
// 开始得慢，结束得快，就像重物落下一样
ease: "power1.out"
// start fast and end slower, like a rolling ball slowly coming to a stop
// 开始得快，结束得慢，就像一个滚动的球慢慢停下来
ease: "power1.inOut"
// start slow and end slow, like a car accelerating and decelerating
// 起步慢，结束也慢，就像汽车在加速和减速