Zombie driver meets survivivors type of the game? I'm in!

I love the blood splat remaining where a zombie died! 

Things to add that would be a big win:

• Sound control and some variation in shooting sound - currently it is tiring for longer sessions
• Description for upgrades/squads could be beneficial
• Balancing - small zombies are so tough...
• Some environmental elements so we can easily tell which direction and what speed are we driving