"my lil' sandbox game" is a websim website which was made by blackkitten, where you can do whatever you want, as the name says, it's a little sandbox game. The game has a lot of mechanics, defining the essence of a true Sandbox Game.
"Mixing" is a feature in the game where you can mix two elements or more to make a new one.
Guidebook:
Another game feature is "Modding"
blah blah blah