html,
body {
  height: 100%;
  margin: 0;
}

body {
  --size: 15px;
  --color: black;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  color: var(--color);
  background-color: #ff8585;
  background: linear-gradient(
    162deg,
    rgba(255, 133, 133, 1) 0%,
    rgba(227, 84, 95, 1) 100%
  );
}

footer {
  font-size: 0.8em;
}

@media (min-height: 425px) {
  body {
    --size: 25px;
  }

  footer {
    height: 40px;
    font-size: 1em;
  }
}

.container {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100%;
}

header {
  display: flex;
  justify-content: space-between;
  width: calc(var(--size) * 17);
  font-size: 2em;
  font-weight: 900;
}

.grid {
  display: grid;
  grid-template-columns: repeat(15, auto);
  grid-template-rows: repeat(15, auto);
  border: var(--size) solid var(--color);
}
.tile {
  position: relative;
  width: var(--size);
  height: var(--size);
}
.content {
  position: absolute;
  width: 100%;
  height: 100%;
}

footer {
  margin-top: 20px;
  max-width: calc(var(--size) * 17);
  text-align: center;
}

footer a:visited {
  color: inherit;
}