body {
  position: relative; /* usually the parent, in this case the body element, has position relative so that the absolute positioned child is positioned relative to it */
  height: 100vh; /* 100% of the viewport height */
  margin: 0; /* recommended */
}

h1 {
 font-family: "Lucida Console", "Courier New", monospace;
 position: absolute; /* taken out of the normal flow of the document */
 top: 45%; /* moved down by 50% of the screen height */
 transform: translateY(-70%); /* moved back up (Y axis) by half of its height to achieve the perfect center */
 width: 100%; /* needs to be defined to keep the default block behavior */
 text-align: center;
 margin: 0; /* again, for perfect center */
}

p {
 font-family: "Lucida Console", "Courier New", monospace;
 position: absolute; /* taken out of the normal flow of the document */
 top: 50%; /* moved down by 50% of the screen height */
 transform: translateY(-50%); /* moved back up (Y axis) by half of its height to achieve the perfect center */
 width: 100%; /* needs to be defined to keep the default block behavior */
 text-align: center;
 margin: 0; /* again, for perfect center */
}