@TheFamousRat The error is in his title:
“Random does not contain a definition for ‘RandRange’”. I think you’re following the example for RandomNumberGenerator in the documentation which says that RandRange() is the C# equivalent of rand_range() in gdscript. I’m seeing the same error, and I was able to fix the problem by doing GD.RandRange(...), omitting the Random variable name entirely.