.grid {
    display: flex;
    flex-wrap: wrap;
    border: solid 3px;
    width: 300px;
    height: 300px;
    border-radius:9px;
}
.center{
  margin:auto;
}
.header{
  font-size:4rem ;
  font-family: 'DM Mono', monospace;
  text-align:center;
}
.grid div {
    width: 20px;
    height: 20px;
}

.shooter {
    background-color: grey;
    border-radius: 5px;
}

.invader {
    background-color: violet;
    border-radius: 10px;
}

.boom {
    background-color: red;
    border-radius: 3px;
}

.laser {
    background-color: blue;
    border-radius: 3px;
}