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CSS

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HTML 

              
                <div class="grid-accordion">
  <div class="letter-m fibonacci-grid">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
    <div class="cell4 fibonacci-cell">
    </div>
    <div class="cell5 fibonacci-cell">
    </div>
  </div>
  <div class="letter-o fibonacci-grid">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
    <div class="cell4 fibonacci-cell">
    </div>
  </div>
  <div class="letter-n fibonacci-grid first-n">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
  </div>
  <div class="letter-d fibonacci-grid">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
    <div class="cell4 fibonacci-cell">
    </div>
  </div>
  <div class="letter-double fibonacci-grid">
    <div class="letter-r flrtv fibonacci-grid">
      <div class="cell1 fibonacci-cell">
      </div>
      <div class="cell2 fibonacci-cell">
      </div>
    </div>
    <div class="letter-i fibonacci-grid">
      <div class="cell1 fibonacci-cell">
      </div>
      <div class="cell2 fibonacci-cell">
      </div>
    </div>
  </div>
  <div class="letter-a fibonacci-grid">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
    <div class="cell4 fibonacci-cell">
    </div>
    <div class="cell5 fibonacci-cell">
    </div>
    <div class="cell6 fibonacci-cell">
    </div>
    <div class="cell7 fibonacci-cell">
    </div>
  </div>
  <div class="letter-n fibonacci-grid second-n">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
  </div>
  <div class="question-mark fibonacci-grid">
    <div class="cell1 fibonacci-cell">
    </div>
    <div class="cell2 fibonacci-cell">
    </div>
    <div class="cell3 fibonacci-cell">
    </div>
    <div class="cell4 fibonacci-cell">
    </div>
    <div class="cell5 fibonacci-cell">
    </div>
    <div class="cell6 fibonacci-cell">
    </div>
  </div>
</div>
!

CSS 

              
                :root {
  --black-color: rgb(22 20 19);
  --black-color-alpha: rgb(22 20 19 / 34%);
  --red-color: rgb(253 75 74);
  --blue-color: rgb(38 114 137);
  --blue-color-alpha: rgb(38 114 137 / 21%);
  --yellow-color: rgb(243 183 60);
  --yellow-color-alpha: rgb(243 183 60 / 34%);
  --white-color: rgb(230 210 190);
  --bg-color: rgb(249, 245, 239);
  --gridgap: 0.62vmin;
  --playing-state: paused;
}

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

body {
  width: 100%;
  height: 100vh;
  display: grid;
  place-items: center;
  background-color: var(--bg-color);
}

.grid-accordion {
  width: 89%;
  height: 89vh;
  background-color: var(--black-color);
  border: 2vmin solid rgb(249 245 239);
  box-shadow: inset 21vmin 21vmin 55vmin var(--blue-color-alpha),
    inset -13vmin -13vmin 55vmin var(--blue-color-alpha),
    1vmin 2vmin 5vmin var(--black-color-alpha);
  display: grid;
  grid-template-columns: 33.33% 33.33% 33.33%;
  grid-template-rows: 33.33% 33.33% 33.33%;
  animation: pulse 10s infinite alternate;
  animation-play-state: var(--playing-state);
}

.grid-accordion:hover {
  --playing-state: running;
  cursor: pointer;
}

.grid-accordion:hover .fibonacci-cell {
  box-shadow: none;
}

.fibonacci-grid {
  width: 100%;
  height: 100%;
  display: grid;
  grid-template-columns: auto repeat(13, 1fr) auto;
  grid-template-rows: auto repeat(8, 1fr) auto;
  gap: var(--gridgap);
}

.fibonacci-cell {
  background-color: var(--white-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184),
    inset -21px -21px 55px var(--yellow-color-alpha);
}

.fibonacci-grid:nth-of-type(-n + 3) {
  grid-column: 2 / 5;
  grid-column: 1 / 2;
}

.fibonacci-grid:nth-of-type(n + 4) {
  grid-column: 2 / 3;
}

.fibonacci-grid:nth-of-type(5) {
  grid-row: 2 / 4;
}

.fibonacci-grid:nth-of-type(n + 6) {
  grid-column: 3 / -1;
}

.fibonacci-grid:nth-of-type(4) {
  grid-row: 1 / 2;
}

.fibonacci-grid:nth-of-type(6) {
  grid-row: 1 / 2;
}

.fibonacci-grid:nth-of-type(7) {
  grid-row: 2 / 3;
}

/*letter a*/

.letter-a .cell1 {
  grid-column: 10 / span 5;
  grid-row: 5 / span 5;
  background-color: var(--blue-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 34%),
    inset -21px -21px 34px rgb(29 88 106);
}

.letter-a .cell2 {
  grid-column: 2 / span 5;
  grid-row: 2 / span 3;
  border-top-left-radius: 100%;
}

.letter-a .cell3 {
  grid-column: 2 / span 5;
  grid-row: 5 / span 5;
  border-top-left-radius: 75% 50%;
  border-bottom-left-radius: 75% 50%;
}

.letter-a .cell4 {
  grid-column: 10 / span 5;
  grid-row: 2 / span 3;
  border-top-right-radius: 100%;
}

.letter-a .cell5 {
  grid-column: 7 / span 3;
  grid-row: 2 / span 2;
}

.letter-a .cell6 {
  grid-column: 7 / span 3;
  grid-row: 5 / span 2;
}

.letter-a .cell7 {
  grid-column: 7 / span 3;
  grid-row: 8 / span 2;
}

/*letter d*/

.letter-d .cell1 {
  grid-column: 10 / span 5;
  grid-row: 2 / -2;
}

.letter-d .cell2 {
  grid-column: 2 / span 5;
  grid-row: 2 / -2;
  border-top-left-radius: 100% 50%;
  border-bottom-left-radius: 100% 50%;
}

.letter-d .cell3 {
  grid-column: 7 / span 5;
  grid-row: 2 / span 2;
  border-top-right-radius: 100%;
  grid-column: 7 / span 3;
}

.letter-d .cell4 {
  grid-column: 7 / span 3;
  grid-row: 5 / span 5;
  background-color: var(--blue-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 34%),
    inset -21px -21px 34px rgb(29 88 106);
}

/*letter i*/

.letter-i {
  grid-template-columns: auto repeat(5, 1fr) auto;
}

.letter-i .cell1 {
  grid-column: 2 / -1;
  grid-row: 2 / span 3;
  background-color: var(--yellow-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 55%),
    inset -13px -13px 34px rgb(241 169 23);
}

.letter-i .cell2 {
  grid-column: 2 / -1;
  grid-row: 5 / span 5;
  background-color: var(--yellow-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 55%),
    inset -13px -13px 34px rgb(241 169 23);
}

/*letter m*/

.letter-m .cell1 {
  grid-column: 4 / span 3;
  grid-row: 2 / span 2;
  border-top-left-radius: 100%;
}

.letter-m .cell2 {
  grid-row: 2 / span 2;
  border-top-left-radius: 100%;
  grid-column: 7 / span 3;
  border-top-left-radius: 100%;
}

.letter-m .cell3 {
  grid-column: 10 / span 5;
  grid-row: 2 / -2;
  border-top-right-radius: 100% 50%;
}

.letter-m .cell4 {
  grid-column: 2 / span 5;
  grid-row: 2 / -2;
  border-top-right-radius: 100% 50%;
}

.letter-m .cell5 {
  grid-column: 7 / span 3;
  grid-row: 2 / span 8;
  border-top-right-radius: 100% 50%;
}

/*letter n*/

.letter-n .cell1 {
  grid-column: 2 / span 5;
  grid-row: 2 / -2;
}

.letter-n .cell2 {
  grid-column: 5 / span 5;
  grid-row: 2 / span 2;
  border-top-left-radius: 100%;
  grid-column: 7 / span 3;
}

.letter-n .cell3 {
  grid-column: 10 / span 5;
  grid-row: 2 / -2;
  border-top-right-radius: 100% 50%;
}

/*letter o*/

.letter-o .cell1 {
  grid-column: 2 / span 5;
  grid-row: 2 / -2;
  border-top-left-radius: 100% 50%;
  border-bottom-left-radius: 100% 50%;
}

.letter-o .cell2 {
  grid-column: 10 / span 5;
  grid-row: 2 / -2;
  border-top-right-radius: 100% 50%;
  border-bottom-right-radius: 100% 50%;
}

.letter-o .cell3 {
  grid-column: 7 / span 3;
  grid-row: 2 / span 2;
}

.letter-o .cell4 {
  grid-column: 7 / span 3;
  grid-row: 8 / span 2;
}

/*letter r*/

.letter-r .cell1 {
  grid-column: 2 / span 5;
  grid-row: 2 / -2;
}

.letter-r .cell2 {
  grid-column: 7 / span 3;
  grid-row: 2 / span 2;
  border-top-left-radius: 100%;
}

/*question-mark ?*/

.question-mark .cell1 {
  grid-column: 2 / span 5;
  grid-row: 2 / span 3;
  border-top-left-radius: 100%;
}

.question-mark .cell2 {
  grid-column: 7 / span 3;
  grid-row: 2 / span 2;
}

.question-mark .cell3 {
  grid-column: 10 / span 5;
  grid-row: 2 / span 5;
  border-top-right-radius: 100% 50%;
  border-bottom-right-radius: 100% 50%;
}

.question-mark .cell4 {
  grid-column: 2 / span 5;
  grid-row: 5 / span 2;
  border-top-left-radius: 100%;
}

.question-mark .cell5 {
  grid-column: 7 / span 3;
  grid-row: 5 / span 2;
}

.question-mark .cell6 {
  grid-column: 2 / span 5;
  grid-row: 7 / span 3;
  background-color: var(--blue-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 34%),
    inset -21px -21px 34px rgb(29 88 106);
}

.letter-double {
  grid-template-columns: repeat(13, 1fr);
  grid-template-rows: repeat(8, 1fr);
}

.letter-double .letter-r {
  grid-column: 1 / -1;
  grid-row: 1 / -1;
}

.letter-double .letter-i {
  grid-column: 9 / -1;
  grid-row: 1 / -1;
  margin-left: calc(var(--gridgap) * -1);
}

.first-n .cell1 {
  background-color: var(--red-color);
  box-shadow: inset 13px 13px 34px rgb(192 189 184 / 34%),
    inset -21px -21px 34px rgb(253 36 35);
}

@keyframes pulse {
  25% {
    grid-template-columns: 80% 10% 10%;
    grid-template-rows: 15% 25% 60%;
  }

  50% {
    grid-template-columns: 20% 70% 10%;
    grid-template-rows: 70% 15% 15%;
  }

  60% {
    grid-template-columns: 20% 70% 10%;
    grid-template-rows: 30% 55% 15%;
  }

  75% {
    grid-template-columns: 20% 15% 65%;
    grid-template-rows: 10% 75% 15%;
  }

  100% {
    grid-template-columns: 15% 10% 75%;
    grid-template-rows: 15% 10% 75%;
  }
}
!

JS 

              
                /*
 * Hover to animate - only in Firefox!
 * https://css-tricks.com/mondrian-art-in-css-from-5-code-artists/#comment-1788812
 */
!
999px

Console