Thanks for playing. We actually wanted to add some sort of dynamic zombie spawning to the game to make it easier or harder depending on how well you were doing but other mechanics and time restraints got in the way. Goes to show how important difficulty adjustments are. As for the firing delay issue, the game does have a "reload" mechanic after two shots shown by the shells in the bottom corner. Though, to be honest, a sound effect would probably make that clearer. If that wasn't the issue could you let us know?