Space Chem!It's always a great moment to come across an indie game that's unique and refreshing.
In 2011, the first game in this category is Space Chem (credit RPS, where I first heard about the game). Here's the description from the game's website:
Zachtronics Industries is back with an ambitious new design-based puzzle game. 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.
Quintin Smith's RPS post gives this description:
SpaceChem is about creating circuits for chemicals to travel down, aligning them in certain ways or shunting them through machinery to create the molecules you need. Wait- that sounds terribly dry. Let me try again.
SpaceChem is a game where you build fabulous contraptions. It’s about getting stuck into a massive puzzle, laughing at the optimism of what’s expected of you, and then finally applying what might be the finishing touch to your engine and cheering as it works. There’s even a strange element of not simply feeling like a gamer, but a scientist. You’re constantly having these little ‘Eureka!’ moments and folding them into a level to make for a more efficient machine.
That's a wonderful description of this game--it's very clever, and it makes your brain work. Building the "chemistry circuit", then watching it run, then modifying it so it actually works (in my case, at least) is almost hypnotic.
It's very challenging, very fun, and the game is full of personality. There's a demo as well as a trailer here, and it's well worth checking out.