These sorts of games are cool because you're playing both sides--winning with one makes it harder to win with the other, so the challenge sort of naturally increases! But if you shoot in a straight line as the ghost, you can survive the wave as the hero by standing still off to the side, which makes it easy for the ghost to kill the hero in the next round, etc., so you can easily live for a while. I think changing the win conditions slightly would encourage the player to lay out more intense attack patterns, which would ramp up the challenge! I think this game has a lot of potential outside of the jam!