A very unique and interesting game... 4/5, the only thing I would suggest would be to make it so that the mouse doesn't follow the scrolling of the screen. It kind of messes up the timing that I have.
Awesome game, and I only have one recommendation - make it so that when a zombie/soldier jumps on your car and you knock them off/shoot them, it counts toward your combo. There has been many times where I am on a 5 or 6 combo and a zombie gets on my car, when I could've had at least 3 more zombies. +1 if you agree so the Dev can see.
For Hard Badge: View Credits before clicking Play, return to menu and click play. Finish first three levels. On the fourth level, pick up the elephant with your mouse and bring him to the pipe, but dont let go. Keep moving him around in the pipe, and you will continue all the way to the end in 1-2 min.