Do you think increase the damage of the first gun would do ? I can get to more than round 10 as I was making the game as I was playing it a lot so the beginning seems easy as we can just turn around in the first room, make money until wave 5-6 then go through some door to unlock the upgrade. I will increase the gun damage and reduce the speed of the zombie in the beginning it should be easier, I will check right now ;)