SpaceChem is an obscenely addictive, design-based puzzle game about building machines and fighting monsters in the name of science! Take on the role of a Reactor Engineer working for SpaceChem, the leading chemical synthesizer for frontier colonies. Construct elaborate factories to transform raw materials into valuable chemical products! Streamline your designs to meet production quotas and survive encounters with the sinister threats that plague SpaceChem.

Zarius says

10/10 - Agree (2) Disagree

Brilliant if you like puzzle games - very complex interactions and an intriguing (text-based) story that unfolds as you play. Love linking the factories together.

And just when you think there's nothing new it chucks another cool game mechanic at you.