It would be nice to have some horizontal movement in the sub, however I get that the idea is to continue downwards. Was there a change in the number of beasts the further down you go? It seemed to be quite consistent with how many were appearing throughout. Maybe having waves of enemies (excuse the pun) would be more fun when you reach certain depths to add a bit of challenge, and an extra objective would give it more purpose. Good pixelart considering there were so many assets to make!