.grid-container {
  height: 100vh;
  display: grid;
  grid-gap: 1vmin;   
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  grid-template-areas:
        "h h h"
        ". c ."
        "f f f";
  align-items: center;
  justify-content: 
}

@media screen and (max-width: 640px) {
    .grid-container {
        grid-template-areas:
          "h h h"
	        ". c ."
	        "f f f";
    }
}

.header {
    grid-area: h;
}

.content {
    grid-area: c;
    justify-self: center;

}

.footer {
   grid-area: f;
}

.grid-container > div {
}