实现一个宽高自适应的正方形

.square {width: 10%;height: 10vw;background: tomato;
}

.square {width: 20%;height: 0;padding-top: 20%;background: orange;
}

.square {width: 30%;overflow: hidden;background: yellow;
}
.square::after {content: '';display: block;margin-top: 100%;
}