.aa>img {
    /* 设置过度的属性，all代表所有属性都可以过度 */
    transition-property: all;
    /* 设置过度持续的时间 */
    transition-duration: 0.5s;
}

.aa>img:nth-child(2) {
    transition-delay: 0.5s;
}

.aa>img:nth-child(3) {
    transition-delay: 1s;
}

.aa>img:nth-child(4) {
    transition-delay: 1.5s;
}

.aa>img:nth-child(5) {
    transition-delay: 2s;
}

.aa>img:nth-child(6) {
    transition-delay: 2.5s;
}

.aa>img:nth-child(7) {
    transition-delay: 3s;
}

.aa>img:nth-child(8) {
    transition-delay: 3.5s;
}

.aa>img:nth-child(9) {
    transition-delay: 4s;
}

.aa>img:nth-child(10) {
    transition-delay: 4.5s;
}

.aa>img:nth-child(11) {
    transition-delay: 5s;
}

.aa>img:nth-child(12) {
    transition-delay: 5.5s;
}