Use the space bar to shoot. Use the left and right arrows to move the spaceship.
I didn't want the bullet to move left and right once it had been fired, so I added an IF statement that tested the Y value of the bullet. If the bullet is moving upwards, Y will be greater than -138 (the start position) and under these conditions the bullet can't be moved left and right. There might be an easier way to do this!!!!
