@ pew I honestly haven't dealt with physics yet in 3DGS. But I'm sure I can figure it out. You just want a tank to be able to drive on terrain you created. Are you using any terrain programs? If you keep getting invalid name, just try to name it something else. See if that helps.

@King You saved it as simpleroom, and also made sure you use default settings when trying to run? And you did add the scripts as stated? I'm guessing your referring to the first video? Hmm. Black box. Did you be sure to position the position of your camera, or the position of your player inside the geometry? And made sure nothing was outside? And did you add your own lights?