Thank you for playing and reviewing this game! It means a lot. Regrettably, I had not much time to develop this game jam entry. I developed it in one night before the deadline, with about 16 hours total. Thus, I did not have much time to optimize the zombie spawning and overall performance.I am sorry that you could not enjoy this game. But I will surely optimize it in the next update of the game. Thank you again for trying it out!