I bought SpaceChem in the Steam summer sale, sort of on a whim. I had read some good reviews and knew that Robin Walker (of Valve) recommended SpaceChem (and only SpaceChem). Of course, the game also has a cross-promotion with Team Fortress 2, which helped. But before the sale, I had held off on purchasing the game, or even playing the demo. "It's a chemistry game," I thought. After devoting 8 months of my life to organic chemistry and barely making it out alive, I didn't think I would ever want to play a game about chemistry.

But SpaceChem isn't a chemistry game; chemistry just happens to be the game's setting. You don't need any knowledge of chemistry to play SpaceChem. It's also unlikely that you would learn anything more than some cursory knowledge about elements, molecules, bonding, etc.

SpaceChem was created by Zachtronic Industries/Zachary Barth, who also created The Codex of Alchemical Engineering (a similar game with a different setting) and Infiniminer (the game that inspired Notch to create Minecraft). Despite the chemistry theme, SpaceChem is really a game of visual programming. You are repeatedly tasked with taking one or more chemical inputs (an atom of a given element, a molecule, etc.), converting them to a specified output, and moving them to the correct output location.

This process is accomplished by directing two "waldos," remote operators that move and act according to instructions you place on each level's grid. The red and blue waldos only respond to instructions of the same color, and only one instruction of each color can occupy a given square on the grid. At first, the available instructions are simple: movement, molecule input/output, grab/drop, rotate, sync (with other waldo). As the game progressed, additional tools and instructions are added: bond addition/removal, "quantum teleportation," sensor (redirects waldo if it is holding a specified element), flip/flop (sends waldo in alternating directions), fusion/fission, etc.


The levels themselves follow a similar theme of increasing complexity. In the beginnings of the game (and often the beginning of each "world'), levels are just...levels. You take one or two inputs, use your waldos to create one or two outputs, and output them. That is hard enough in some cases, but SpaceChem quickly expands this concept to great effect. Missions quickly appear that take place at a whole new level. Inputs and outputs appear on overland terrain; the inputs must be routed through reactors and transported to the outputs.

But what is a reactor? Nothing more than what you had previously thought of as a "level," except now you can potentially control the inputs and outputs. The normal missions already had great variability in possible solutions, but once SpaceChem introduces these reactors, the solutions become almost endless. New problems are introduced, too, though. All the inputs and outputs in each reactor occur in real-time. Outputs can be backed up, inputs can come too slowly for your mechanism to function correctly, etc. If anything goes wrong, your entire reactor system grinds to a halt.

Overcoming these problems, slowly and incrementally, is really what makes SpaceChem's challenge fun. You start with an idea and must constantly tweak and improve the mechanism until everything works. Fixing one problem can introduce or reveal a new problem. So you go back and fix that one. Your entire solution may work except for a matter of timing, so next you play around with sync instructions or extending or shortening paths.


Finally everything will come together to work flawlessly; the sense of satisfaction at that point is great. Even better, SpaceChem records stats for all solutions: the number of cycles (duration), the number of reactors (if applicable), and the number of symbols used. All the data is presented in simple graphs at the end of each level so you can compare your results with the rest of the community.

SpaceChem also includes an option to record a video of your solution which can then be saved to your desktop or uploaded to YouTube from within the game. The YouTube functionality is especially nice, saving everyone the trouble of recording, encoding, and uploading, and also provides for a substantial collection of videos for each level. Whether you want a solution for a level you're stuck on, or more indirect inspiration, or just to look at other solutions to see how they vary, you'll be able to find plenty of videos to watch.

I do think the recording feature could use some improvements. For levels with reactors, no recording is made of the mechanisms within the reactors. You can still see what is going on in the zoomed out view, but only enough to get a general idea. It would also be nice if recorded videos could be saved to a designated folder instead of simply the desktop.

I'm really not very far into SpaceChem; I'm only about to finish the 3rd world of eight. I have also played some user-made levels in the ResearchNet (for a Steam summer camp ticket) and some levels in the Corvi DLC (won from the Steam summer camp prize booth). I've also finished two of three Team Fortress 2 themed levels; each level grants some crafting ingredients in TF2 that can be used to craft the Fishcake and the SpaceChem Pin. The first two levels give the ingredients for the Fishcake so I only have that item so far.


I already know though that I am going to be spending a lot more time in SpaceChem. Finding a game that is actually challenging is rare these days, so now I feel compelled to see how many levels I can beat without help. Even if I do somehow manage to finish all the levels, I doubt I'll be done with SpaceChem. There will be improvements to be made in previous solutions, more ResearchNet levels, and probably additional DLC to consider purchasing.

I definitely recommend trying out the SpaceChem demo before making a purchase. The game is certainly not for everyone. But for a specific subset of players that appreciates the gameplay and style, SpaceChem is a great purchase. With unique gameplay, great replayability, lots of challenging content, quality sound and visual design, and good post-release support, SpaceChem is worth a look.