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body {
  display: flex;
  height: 100vh;
  margin: 0;
}
div {
  flex: 1;
}
div:nth-child(1) {
  background: hsl(0 0% 0%);
}
div:nth-child(1) {
  background: hsl(0 0% 10%);
}
div:nth-child(2) {
  background: hsl(0 0% 20%);
}
div:nth-child(3) {
  background: hsl(0 0% 30%);
}
div:nth-child(4) {
  background: hsl(0 0% 40%);
}
div:nth-child(5) {
  background: hsl(0 0% 50%);
}
div:nth-child(6) {
  background: hsl(0 0% 60%);
}
div:nth-child(7) {
  background: hsl(0 0% 70%);
}
div:nth-child(8) {
  background: hsl(0 0% 80%);
}
div:nth-child(9) {
  background: hsl(0 0% 90%);
}
div:nth-child(10) {
  background: hsl(0 0% 100%);
}

External CSS

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External JavaScript

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