style.styl

html
body
  margin 0
  width 100%
  height 100%
  overflow hidden
  background slategrey
  cursor default
  font-family sans-serif

  .start-button
    display block
    position fixed
    color white
    border none
    opacity 0.5
    top 0
    left 0
    width 100%
    height 100%
    z-index 2
    background black
    transition opacity 1s
    transform translateZ(0)
    font-size 100px
    cursor pointer

    &.fade-out
      opacity 0

  .worlds
    position fixed
    left 0
    bottom 0
    z-index 3
    opacity 0.3
    padding 10px
    transition opacity 0.5s

    &.fade-out
      opacity 0

    &:hover
    &.start
      opacity 0.6

    .world-link
      display inline-block
      width 30px
      height 30px
      z-index 2
      background transparent
      border none
      color white
      cursor pointer
      font-size 16px
      text-decoration none
      text-align center
      opacity 0.5
      transition opacity 0.2s

      &:hover
        opacity 1

      &:focus
        outline none

  .controls
    position fixed
    right 0
    bottom 0
    z-index 1
    opacity 0.3
    padding 10px
    transition opacity 0.5s

    &.fade-out
      opacity 0

    &:hover
      opacity 0.6

    button
      width 40px
      height 40px
      z-index 2
      background transparent
      border none
      color white
      cursor pointer
      font-size 20px
      opacity 0.5
      transition opacity 0.2s

      &:hover
        opacity 1

      &:focus
        outline none

    .audio-button.off
      text-decoration line-through