main.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: "Press Start 2P", cursive;
}

body {
  background-color: blue;
}

.app {
  display: grid;
  grid-template-columns: 644px 1fr;
  gap: 10px;
}

.grid {
  width: 604px;
  height: 604px;
  margin: 20px;
  border: 2px solid white;

  display: grid;
  grid-template-columns: repeat(auto-fit, 40px);
  grid-auto-rows: 40px;
}

.grid > div {
  width: 40px;
  height: 40px;

  background-position: center center;
  background-repeat: no-repeat;
  background-size: contain;
}

.spaceship {
  background-image: url("./images/spaceship.png");
}

.laser {
  background-image: url("./images/projectile.png");
}

.alien {
  background-image: url("./images/alien.png");
}

.hit {
  background-image: url("./images/explosion.png");
}

.message {
  position: absolute;
  top: 200px;
  left: 200px;
  width: 200px;
  height: 100px;
  background-color: white;
  opacity: 85%;
}

.message h1 {
  color: blue;
  text-align: center;
  line-height: 50px;
}

.scoreboard {
  margin: 20px;
  color: white;
}

.scoreboard > * {
  margin: 20px;
}