I'm not very good at making games for one thing. Secondly, I have no idea why it has an open roof. So I know that this game sucks. Rate this up so people can read it. Thanks. :)
To get the hard badge you have to get the tank and the golden gun. Also have at least 30 nukes. Shoot him up with full power towards the sky. He should get about 1500 ft high; when he's above the skyline, wait for him to come down and then let him bounce. When the turtle comes down from the skyline after that, shoot it again. Repeat this process until all your bullets are gone. After that, use as many nukes as possible, one after another. If you get any more ammo, do the same as you did at the start. Hope that helps!