Excellent Game. I wanted to pull out a similar game but due to lack of time i was not able to implement the bullets following the mouse cursor position, i was not able to stop the game once the player was hit by a zombie, rather it removes the player, and was not able to implement the logic for the enemies to follow the player's face position. I know that there is a atan2 function in GDScript that allows us to do so. Overall i like the look and feel of your game better and the reload mechanism, where in i have implemented the infinite ammo. Keep up the good Work :)