Chalk. It doesn't just go lovely with a bit of cheese, you can also use it to draw on things. Blackboards, for example. Walls, for another. If you do the latter in the aptly named Chalkboard, you'll cut bits out of the environment, and solve puzzles.
Neat idea, isn't it? And it's used in a handful of puzzles that unfold in beautiful ways, but that are unlikely to trouble you too much. This is a decidedly chill puzzle game with a huge margin for error. It's very sweet, though I do wish the central mechanic had been explored in a bit more depth.
This isn't the next mind-blowing puzzle game, but it is a lovely puzzle toy where you feel something like a wizard, shifting the fabric of an ambient, chalky world. You can grab Chalkboard from here. (Thanks, Warp Door.)
For more great free experiences, check out our roundup of the best free PC games.