Thank you so much for playing! I appreciate the constructive feedback. I considered doing a scoring system that works as follows: you start the game with an 'A' rank. Every time you get turned into a ghost, it drops a letter grade (with F being the worst you can get). So, if you can make it all the way through a level without getting hit, you will finish with an A ranking. Perhaps this would have made the game more engaging to play, as I see your point that the only reason to continue playing as it is now is to get to the next level / next wave of enemies.
I will definitely play and rate your game! It's in my queue :) thanks again for your feedback.