* {
  margin: 0;
  padding: 0;
}
.wrapper {
  border: 5px solid black;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  height: 600px;
  width: 600px;
  background: url('images/background.png');
}

canvas,
#grass {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
}

#grass {
  width: 600px;
  height: 600px;
  background: url('images/grass.png');
}