css flex center horizontally and vertically

display: flex;
align-items: center;
justify-content: center;

.Aligner {
  display: flex;
  align-items: center;
  justify-content: center;
}

.Aligner-item {
  max-width: 50%;
}

.Aligner-item--top {
  align-self: flex-start;
}

.Aligner-item--bottom {
  align-self: flex-end;
}

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

.center {
  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  -ms-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}