Sandbox idea

I want to make a sand box kind of game, more for testing out my skills as a programmer than anything else, and also a place where I can just hang out by myself in an interesting place. This will primarily be a VR thing, and I’m wondering if people have done this kind of thing before? I want to be able to test out the various physics involved in setting up something like a race car, or a gun and making it seem realistic, and maybe even adding myself a game of some sort in the process to goof off in. I don’t want it to just be a mess of code though either. Think something like what think space is supposed to be except that it would be for more than just writing down ideas. I also saw another game that basically let you craft things and do what you want with it, but I don’t remember the game’s name. Is this a workable idea?