style.css

/* 这是引入了一些字体 */
@import url('https://fonts.googleapis.com/css?family=Poppins:100,200,300,400,500,600,700,800,900'); 

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Poppins', sans-serif;
}

/* :root 的用法不会的看这里 https://blog.csdn.net/weixin_51123974/article/details/122311909 */
:root {
  --clr: #222327;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: var(--clr);
}

.navigation {
  position: relative;
  width: 400px;
  height: 70px;
  background: #fff;
  display: flex;
  justify-content: center;
  align-items: center;
  border-radius: 10px;
}

.navigation ul {
  display: flex;
  width: 350px;
}

.navigation ul li {
  position: relative;
  list-style: none;
  width: 70px;
  height: 70px;
  z-index: 1;
}

.navigation ul li a {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  width: 100%;
  text-align: center;
  font-weight: 500;
}

.navigation ul li a .icon {
  position: relative;
  display: block;
  line-height: 75px;
  font-size: 1.5em;
  text-align: center;
  transition: 0.5s;
  color: var(--clr);
}

.navigation ul li.active a .icon {
  transform: translateY(-32px);
}

.navigation ul li a .text {
  position: absolute;
  color: var(--clr);
  font-weight: 400;
  letter-spacing: 0.05em; /* 字符间距 */
  transition: 0.5s;
  opacity: 0;
  transform: translateY(20px);
}

.navigation ul li.active a .text {
  opacity: 1;
  transform: translateY(10px);
} 

.indicator {
  position: absolute;
  top: -50%;
  width: 70px;
  height: 70px;
  background: #29fd53;
  border-radius: 50%;
  border: 6px solid var(--clr);
  transition: 0.5s;
}

.indicator::before{
  content: '';
  position: absolute;
  top: 50%;
  left: -22px;
  width: 20px;
  height: 20px;
  background: transparent;
  border-top-right-radius: 20px;
  box-shadow: 1px -10px 0 0 var(--clr);
}

.indicator::after{
  content: '';
  position: absolute;
  top: 50%;
  right: -22px;
  width: 20px;
  height: 20px;
  background: transparent;
  border-top-left-radius: 20px;
  box-shadow: -1px -10px 0 0 var(--clr);
}

.navigation ul li:nth-child(1).active ~ .indicator {
  transform: translateX(calc(70px * 0));
}
.navigation ul li:nth-child(2).active ~ .indicator {
  transform: translateX(calc(70px * 1));
}
.navigation ul li:nth-child(3).active ~ .indicator {
  transform: translateX(calc(70px * 2));
}
.navigation ul li:nth-child(4).active ~ .indicator {
  transform: translateX(calc(70px * 3));
}
.navigation ul li:nth-child(5).active ~ .indicator {
  transform: translateX(calc(70px * 4));
}