Simple concept that was well executed! I liked how you added effects and changes in pitch to the sfx for the player feedback, that was pretty cool. I also agree that background music would really elevate this game more. I also think it would've been cool if the monsters maybe switched directions or took different paths across the screen during points of the countdown, I think that could increase the replayablility of the game, especially if it was randomized. But regardless, for 2h this is super well done, and my best score was 350 :)