SpaceChem, the classic Zachtronics design-based puzzle game not only got a sweet update recently to improve the tech behind the game, it's also now super easy to grab the updated community version.
There's no doubt that SpaceChem is a good game, if you're a fan of puzzle games that require you to design special solutions across mind-bending puzzles it's a great choice. It is missing some features though that they added to their later games, like allowing you to keep multiple solutions to each puzzle to test more easily.
Some time ago the SpaceChem Community Edition was announced, with approval from Zachtronics a few dedicated people banded together to upgrade the game with an unofficial patch. With blessing from Zachtronics, it's now being distributed directly on Steam. All you need to do is opt into the 'community-edition' Beta by right clicking the game on Steam, going to Properties and then select it in the Betas tab.
What does it actually give you? You get a small UI adjustment inspired by Exapunks, letting you load a level and then open a solution picker to create and pick from your designs. You can also export and import solutions to puzzles, added keyboard accessibility controls and a number of other enhancements some of which are still highly experimental.