maybe im just a jr programmer and I don't know how to solve that,but your player will just directly go into the terrain instead of being blocked by the terrain.Also there are some problems about collisions.In the speed acceleration normally I just multiply the speed by a special formula.And I would like to rotate the player but the cube just totally not responding to my input.But I still added some basic code in your game and hope the next dev can solve the error of collision in the script