Never played that game. That was before my time :D
Regarding the difficulty. That's a very hard topic to get right because of the wide range of gamers from casual to pro. In addition, getting it right during a game jam is even harder. We tried our best. It also depends a little on the rng for the enemies to spawn. If you get lots of green ones then the game will not be much more difficult. But getting shooter enemies will make it harder very fast :D