app.scss

* {
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.switch {
  position: relative;
  display: inline-block;
  width: 120px;
  height: 52px;
  border-radius: 40px;
  background-color: red;
  input {
    opacity: 0;
    width: 0;
    height: 0;

    &:checked + .slider {
      .text:nth-of-type(2) {
        color: black;
      }
      .text:nth-of-type(1) {
        color: white;
      }
    }

    &:checked + .slider:before {
      transform: translateX(64px);
    }
  }

  .slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: transparent;
    transition: 0.2s;
    z-index: 1;

    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 10px 10px 10px;
    .text {
      font-size: 17px;
      &:nth-of-type(1) {
        color: black;
      }
      &:nth-of-type(2) {
        color: white;
      }
    }
    &::before {
      position: absolute;
      content: "";
      height: 46px;
      width: 46px;
      left: 5px;
      top: 2px;
      border-radius: 50%;
      background-color: white;
      transition: 0.4s;
      z-index: -1;
    }
  }
}