Answers for "the Simplest Way To Center Elements Vertically And Horizontally"

css center horizontally and vertically

.parent {
  position: relative;
}
.child {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

css center vertically and horizontally

body {
	display: flex;
	min-height: 100vh;
	flex-direction: column;
	justify-content: center;
	align-items: center;
}
/* to make "align-items: center" work: use "min-height: 100vh;"
100vh = 100% Viewport Height */