Tetris Animation

<div class="tetris">
  <div class="tetris__block">
    <span class="tetris__block-span"></span>
    <span class="tetris__block-span"></span>
    <span class="tetris__block-span"></span>
    <span class="tetris__block-span"></span>
  </div>
</div>

@keyframes shift {
  0% {
    transform: translate(0, 0);
  }
  to {
    transform: translate(0, 24px);
  }
}

@keyframes movedown {
  0% {
    transform: translate(0, 24px);
  }

  to {
    transform: translate(96px, 288px);
  }
}

@keyframes movedown1 {
  0% {
    transform: translate(0, 24px);
  }

  to {
    transform: translate(-96px, 288px);
  }
}

@keyframes movedown2 {
  0% {
    transform: translate(0, 24px) rotateZ(90deg);
  }

  to {
    transform: translate(24px, 288px) rotateZ(360deg);
  }
}

@keyframes movedown3 {
  0% {
    transform: translate(0, 24px) rotateZ(-270deg);
  }

  to {
    transform: translate(-11px, 276px) rotateZ(270deg);
  }
}

@keyframes colortetris {
  0% {
    background: linear-gradient(to top, var(--border) 0, var(--bg) 24px)
      no-repeat;
  }

  to {
    background: linear-gradient(to top, var(--screen) 0%, var(--screen) 24px)
      no-repeat;
  }
}

/* Block: tetris */
.tetris {
  --border: var(--theme-text-color);
  --bg: var(--theme-base-color);
  --screen: var(--theme-bg-color);
  display: block;
  position: relative;
  height: 288px;
  width: 289px;
  background: var(--screen);
  box-shadow: 0 0 0 1px var(--border) inset;
  overflow: hidden;
}

/* Element: tetris__block */
.tetris__block {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: block;
  font-size: 1.5em;
  text-align: center;
  letter-spacing: 0.1em;
  line-height: 3;
}
.tetris__block::before {
  content: '';
  height: 24px;
  width: 287px;
  position: absolute;
  bottom: 0;
  left: 1px;
  z-index: 1;
}
/* Element: tetris__block-span */
.tetris__block-span {
  position: absolute;
  top: -24px;
  left: 96px;
  height: 24px;
  width: 96px;
  box-shadow: 1px -1px 0 0 var(--border);
  background:
    repeating-linear-gradient(0deg, var(--border) 0 1px, transparent 1px 24px),
    repeating-linear-gradient(90deg, var(--border) 0 1px, transparent 1px 24px)
      var(--bg);
}

/* Modifiers for specific spans */
.tetris__block-span:nth-of-type(3) {
  width: 72px;
}

.tetris__block-span:nth-of-type(4) {
  width: 48px;
}

.tetris__block-span:nth-of-type(3)::before,
.tetris__block-span:nth-of-type(4)::before {
  content: '';
  height: 24px;
  position: absolute;
  top: -24px;
  background: inherit;
  box-shadow: inherit;
}

.tetris__block-span:nth-of-type(3)::before {
  width: 24px;
  right: 24px;
}

.tetris__block-span:nth-of-type(4)::before {
  width: 48px;
  left: 24px;
}

/* Animations */
.animation .tetris__block-span:nth-of-type(1) {
  animation: movedown 1s steps(11, end) forwards;
}

.animation .tetris__block-span:nth-of-type(2) {
  animation: movedown1 1s 1s steps(11, end) forwards;
}

.animation .tetris__block-span:nth-of-type(3) {
  animation: movedown2 1s 2s steps(11, end) forwards;
}

.animation .tetris__block-span:nth-of-type(4) {
  animation: movedown3 1s 3s steps(11, end) forwards;
}

.animation .tetris__block {
  animation: shift 0.5s 4s steps(4, end) forwards;
}
.animation .tetris__block::before {
  animation: colortetris 0.1s 4s steps(7) infinite alternate;
}