mdb-ui-kit/scss/_switches.scss

// http://codepen.io/rosskevin/pen/EPPwRR?editors=110
.switch {
  label {
    position: relative;
    padding-left: $bmd-switch-width + $bmd-switch-label-padding; // absolutely positioned so add the radio size

    .bmd-switch-track {
      position: absolute;
      top: calc-top($line-height-base, $font-size-base, $bmd-switch-height);
      left: 0;
      display: inline-block;
      width: $bmd-switch-width;
      height: $bmd-switch-height;
      cursor: pointer;
      background-image: linear-gradient(
        to right,
        $bmd-switch-unchecked-bg 0%,
        $bmd-switch-unchecked-bg 50%,
        $bmd-switch-checked-bg 50%,
        $bmd-switch-checked-bg 100%
      );
      background-position: 0%;
      background-size: $bmd-switch-width * 2 $bmd-switch-height;
      border-radius: $bmd-switch-width;
      transition: background-position 0.2s ease-in;

      &::after {
        position: absolute;
        top: 50%;
        left: 0;
        display: block;
        align-self: center;
        width: $bmd-switch-handle-size;
        height: $bmd-switch-handle-size;
        content: "";
        background: $bmd-switch-handle-unchecked-bg;
        border-radius: 100%;
        box-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
        transition: left 0.2s ease-in, background-color 0.2s ease-in,
          transform 0.3s ease;
        transform: translateY(-50%);
      }

      // Jelly effect on click
      &:active::after {
        transform: translateY(-50%) scale3d(1.15, 0.85, 1);
      }
    }

    input {
      // Hide original checkbox, but don't use `display: none` to allow focus on it using keyboard
      position: absolute;
      display: block;
      width: 0;
      height: 0;
      opacity: 0;

      &:checked {
        + .bmd-switch-track {
          background-position: -100%;
          &::after {
            left: unquote(
              "calc(100% - #{$bmd-switch-handle-size})"
            ); //calc(100% - $bmd-switch-handle-size);
            background-color: $bmd-switch-handle-checked-bg;
          }
        }
      }

      &:disabled {
        // No jelly effect on disabled switchs
        + .bmd-switch-track:active::after {
          transform: translateY(-50%);
        }

        + .bmd-switch-track {
          cursor: default;
          background: $bmd-switch-disabled-bg;
          &::after {
            background: $bmd-switch-handle-disabled-bg;
          }
        }
      }
    }
  }
}