Three main problems
1) This isn't a sandbox. Don't kid yourself and don't tag it as one.
2) What is in this game is bare minimum. Like, Atari experimentations from 3-4 decades ago bare.
3) Dull, boring, and nothing to it. You say it's a physics simulator, but it doesn't even feel like one.
Final conclusion: This will entertain that one kid from 1097 who stepped through a time portal for about five minutes before he gets bored and learns how to google porn. Other than that, there is nothing to this.