Way too easy.. Laser turrets are either don't cost enough, or do too much damage. I went with 2 machine guns and one laser on each elevator with my last elevator with all lasers upgraded as much as I could afford. I moved that elevator as needed and game over.
Level 1 green tower starts off with 1 damage. Upgraded it does 49 damage.
Comparing the towers damage and upgrade costs.. the white towers completely dominate.
Could use a slightly larger playing area. Perhaps tooltip in tower info about firing rate.
Good game.. Kinda funny though that the objects in the rear view mirror in the intro are coming toward the car when they should be heading away. Car is moving foward and in reverse at the same time apparently :)