Free Garrys Mod is a free variation on the popular Garry's Mod sandbox game, originally an extension of Half-Life 2 and its source engine, where with a map, a character, and a physics gun, the player can do anything, create anything, or build anything, as long as they have the digital resources.

Mods within a mod

Learning to play Gmod can be challenging at first: the physics gun offers many different tools, all with their own menus, and although adding assets is easy, it can take a toll on your computer (and your disk space). If you add out-right mods, you can do things like give yourself infinite health, but those require their own learning, too. On the flip side, you can learn with friends: the game offers multiplayer, both connecting to a host or to a public server, and these options are a great way to play.

Immoderate

Overall, Gmod is an interesting game: it takes some doing to learn how to play in the sandbox, and there's no in-game goals or ending to look for, but there's so much you can do.