Quit a funny game.
At the beginnig I was a little confused cause there is no tutorial... so I havent known that upgrades like "oil" (raise fire-speed) arent permanent... but expensive :/ also the electro-tower could be explained -> it must be placed at both sides of the path to create a electric barrier which deals damage. HINT: after some time youll unlock new towers, which can still be build after a restart. Build a "Crimson" tower after restarting, I got a tower with 2800 damage this way ;)
Nice game, would be awesome if there would be a "speed-up" button.