tic.scss

$color-fade-easing: cubic-bezier(0.4, 0.0, 0.2, 1);

body {
  margin: 0;
  padding: 0;
  font: 16px/1.5 'helvetica neue', sans-serif;
}

main {
  display: flex;
  justify-content: center;

  margin: calc((100vh - 300px) / 2);

  @media (min-height: 100vw) and (max-width: 600px) {
    margin: calc((100vw - 300px) / 2);
  }

  @media (min-width: 600px) and (min-height: 600px)  {
    margin: 150px;
  }
}

.board {
  cursor: default;

  user-select: none;
  -webkit-user-select: none;
  -webkit-tap-highlight-color: transparent;

  display: flex;
  flex-direction: column;

  width: 3 * 100px;
  margin: auto;

  > .row {
    display: flex;
    flex-direction: row;

    width: 3 * 100px;

    > div {
      flex: 0 0 100px;
      height: 100px;

      box-sizing: border-box;
      border: 1px solid #ddd;
      border-bottom: none;
      border-right: none;

      font-size: 32px;
      font-weight: 200;
      text-align: center;
      line-height: 100px;

      &:first-child {
        border-left: none;
      }

      transition: background $color-fade-easing .5s;

      &.active {
        background: rgba(0, 0, 0, 0.1);
        transition: background $color-fade-easing 0s;
      }
    }

    &:first-child > div {
      border-top: none;
    }
  }
}