* {
  box-sizing: border-box;
}

html {
  font-family: Avenir, Helvetica, "Open-Sans", "Helvetica Neue", Arial, sans-serif;
  font-size: 25px;
}

main {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

header {
  display: flex;
  justify-content: center;
}

a {
  background-color: red;
  border-radius: 20px;
  position: absolute;
  width: 300px;
  height: 50px;
  display: flex;
  justify-content: center;
  align-items: center;
  text-decoration: none;
  color: black;
}

img {
  width: 300px;
  transform: rotate(-45deg);
}

ol {
  display: grid;
  grid-template-columns: repeat(5,1fr);
  grid-template-rows: repeat(5,1fr);
  grid-gap: 10px;
  list-style: none;
}

li {
  border: 4px solid black;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100px;
  height: 100px;
}

li span {
  margin-top: 20px;
}

li:nth-child(2), li:nth-child(3), li:nth-child(4) {
  background: linear-gradient(to bottom, white 70%, black 72%, black 75%, green 75%);
}

li:nth-child(6), li:nth-child(7), li:nth-child(8) {
  background: linear-gradient(to left, white 70%, black 72%, black 75%, orange 75%);
}

li:nth-child(10), li:nth-child(11), li:nth-child(12) {
  background: linear-gradient(to top, white 70%, black 72%, black 75%, violet 75%);
}

li:nth-child(14), li:nth-child(15), li:nth-child(16) {
  background: linear-gradient(to right, white 70%, black 72%, black 75%, yellow 75%);
}

li:nth-child(1) span {
  transform: rotate(135deg);
  margin: 0;
}

li:nth-child(5) span {
  transform: rotate(-135deg);
  margin: 0;
}

li:nth-child(9) span {
  transform: rotate(-45deg);
  margin: 0;
}

li:nth-child(13) span {
  transform: rotate(45deg);
  margin: 0;
}

li:nth-child(1) {
  grid-column: 1;
  grid-row: 1;
}

li:nth-child(2) {
  grid-column: 2;
  grid-row: 1;
}

li:nth-child(3) {
  grid-column: 3;
  grid-row: 1;
}

li:nth-child(4) {
  grid-column: 4;
  grid-row: 1;
}

li:nth-child(5) {
  grid-column: 5;
  grid-row: 1;
}

li:nth-child(6) {
  grid-column: 5;
  grid-row: 2;
}

li:nth-child(7) {
  grid-column: 5;
  grid-row: 3;
}

li:nth-child(8) {
  grid-column: 5;
  grid-row: 4;
}

li:nth-child(9) {
  grid-column: 5;
  grid-row: 5;
}

li:nth-child(10) {
  grid-column: 4;
  grid-row: 5;
}

li:nth-child(11) {
  grid-column: 3;
  grid-row: 5;
}

li:nth-child(12) {
  grid-column: 2;
  grid-row: 5;
}

li:nth-child(13) {
  grid-column: 1;
  grid-row: 5;
}

li:nth-child(14) {
  grid-column: 1;
  grid-row: 4;
}

li:nth-child(15) {
  grid-column: 1;
  grid-row: 3;
}

li:nth-child(16) {
  grid-column: 1;
  grid-row: 2;
}

li:nth-child(2) span, li:nth-child(3) span, li:nth-child(4) span{
  transform: rotate(180deg);
  margin: 0;
}

li:nth-child(6) span, li:nth-child(7) span, li:nth-child(8) span {
  transform: rotate(-90deg);
  margin: 0;
}

li:nth-child(14) span,li:nth-child(15) span, li:nth-child(16) span {
  transform: rotate(90deg);
  margin: 0;
}

#centre {
  grid-column: 2 / 5;
  grid-row: 2 / 5;
  width: auto;
  height: auto;
}