I will think about it. Part of the reason why I did not go with absolute directions, was to make the gameplay a bit more unique (as I was limited in terms of graphics).
Truth be told, my initial idea was to actually have a room constantly spinning, but I decided against it lest players get too dizzy. Maybe it was a bad choice.
Another hard decision was removing enemies' "friendly fire", so that they would put more pressure on the player and not eliminate each other. But "friendly fire" does make it possible to find some strategies (passing between enemies so they shoot each other) and it could be possibly more fun to include.
Finally, I am becoming convinced I may have set the max HP too low. Testing it with unlimited hits I found the game becomes a lot more fun and chaotic with loads of enemies - I may have been a bit too hasty to publish it before thinking all this through!