Wikipedia
SpaceChem is an indie puzzle game developed by Zachtronics Industries, based on principles of automation and chemical bonding. In the game, the player is tasked to produce one or more specific chemical molecules via an assembly line by programming two remote manipulators (called "waldos" in the game) that interact with atoms and molecules through a visual programming language. SpaceChem was the developer's first foray into a commercial title after a number of free Flash-based browser games that feature similar puzzle-based assembly problems.
The game was initially released for Microsoft Windows at the start of 2011 via Zachtronics' own website. Though it was initially rejected for sale on the Steam platform, Valve later offered to sell the game after it received high praise from game journalists; further attention came from the game's release alongside one of the Humble Indie Bundles. The game has since been ported to other computing platforms and mobile devices. Reviewers found the game's open-ended problem-solving nature as a highlight of the title. SpaceChem was incorporated into some academic institutions for teaching concepts related to both chemistry and programming.