I noticed Tryko's comment, a solution to make RP amounts fair to players who rarely check back is to both remove the "RP per level" upgrade, have the "coins until next RP" reset with each rebirth, and adjust the RP per level and/or "coins until next level" increase curve.
Hi Robert! You can use WASD to control the tank. If you do - use < > for turret rotation and ? to center the turret ;)