Great game! but i have a little feedback:
what does the 2x firerate mean? does stepping on it increase the firerate or am i supposed to do smth else?
and also the enemies get a tad bit repetitive, so i'd recommend adding more variety. maybe enemies that move faster but are weaker, or vice versa. unless there are other monster and i just didnt get far enough (wave 10)
if there are more, then i'd recommend introducing some of the a little early on. but apart from that this was very cool! (also maybe some rooms could have traps that can hurt the player and the enemies!)