"SpaceChem", explains its website, "is an intriguing, 'problem-solving centric' puzzle game by Zachtronics Industries that combines the logic of computer programming with the scientific domain of chemistry, set in an original science fiction universe."
While accurate and concise, this admittedly sounds a bit dry. But if you're a fan of logic-based puzzles SpaceChem is likely a game that will intrigue you... even if it is, in the loosest sort of way, kind of edutainment.
SpaceChem is all about taking atoms or molecules and transforming them into other atoms or molecules using a process designed by the player. This involves one or more reactors that are programmed to transform these objects.
The cursors are represented as blue and red split circles. The blue cursor only activates blue symbols, the red cursor the red ones; it's possible and sometimes necessary to overlap circuits and symbols.
Two circuits -- colored blue and red -- are available within a reactor, which is represented as a 10x8 grid. It is up to the player to give each circuit its path and to place symbols in that path that cause the circuit to do something desirable. When the simulation is run, a cursor travels along each circuit and will perform an action when it crosses over a symbol.
These circuits typically take "input" atoms or molecules from the left side of the reactor grid, manipulate them, and send them as "output" using the right side of the reactor grid. On the overhead map, there will be one or two pipes going into the left side of the reactor providing the input molecules and one or two pipes leaving the right side of the reactor providing the output.
Atoms/molecules are not permitted to collide with each other within a reactor. Because a reactor contains a very limited amount of space, it soon becomes vital to organize the structure of the routines carefully and to take full advantage of the flexibility and speed that using two circuits can provide. The size of the molecules and the number of operations you must perform on them will largely determine the difficulty.
After the reactor is designed, you press "play", and watch the simulation succeed or fail in a very satisfying fashion. Molecules are slowly rotated, bound or unbound with a subdued color fade animation; the whole thing feels a lot like watching any of the Mr. Rogers' Neighborhood episodes that dealt with industrial manufacturing.
There are no consequences to failure, so you are encouraged to experiment.
More than one reactor can be created and connected on SpaceChem's overhead map to perform complex molecular transformations.
In later levels, SpaceChem requires designs involving more than one reactor and even different types of reactors. These are created on an overhead map. Typically, atoms or molecules arrive in buildings on the left side of the screen. You connect these buildings with pipes to the input(s) of one or more reactors, then connect the output(s) of the reactors to buildings on the right side of the screen which will receive the final product.
For a single-player game, SpaceChem makes excellent use of online features to foster competition. Each puzzle may have multiple solutions, so SpaceChem tracks the number of cycles, reactors, and symbols used for you to solve a puzzle. When you finish a level, it shows you how you rate against other players on a series of bar graphs. Depending on your ego, this can offer sufficient incentive to go back and optimize your solution. There are also a number of user-submitted puzzles available from within the game, with more being added on a periodic basis.
While the chemistry angle is mostly a gimmick to explain the need for disassembling and assembling blocks of matter, SpaceChem most effectively challenges its players to think out and organize solutions in a limited space. It certainly doesn't take long for each win to feel like a real accomplishment.