This is really fun. It's sort of like SpaceChem with online co-op.
You build little circuits of road around a map to gather resources, then build factories in the proper place to ensure your resources get turned into more valuable resources you can sell for more. When you hit your limit on gold, you can either delete some infrustructure (getting your money back with no apparent loss) or just log out and come back later, since your gold will accumulate over time even when logged out.
You start out with a little zone of control around your palace, and you build 'fire towers' to melt ice and gain access to more space and resources (but then you have to build a longer network of roads to get resources back to the palace to make money). The goal is to expand out to the lair of one of several boss monsters on the map and then build a circuit that delivers a specific good to them to defeat them and unlock some randomized treasure (which might unlock cranes for swapping goods, or things like that).
Each map features several players who work together to defeat the bosses, and I think you share treasure if you manage to defeat one. While the day/night cycle (which replenishes resources on the map) takes only a minute, the boss will be available only for a few real-world days, after which the game ends and you have to start a new map. Everything in the game benefits cooperation, and building goods then transferring them to another player to sell ensures both players get a cut of the final sale, so the total gold earned on a traded good is more for both players than if you simply sold it yourself.
The game is financed by microtransactions, which can let you buy some advanced items (like faster roads, more cranes, new factory types) without unlocking them in-game (these seem to be slowly consumed over multiple games, like winning 'stone roads' lets you use them in 40 games before you re-buy them, which seems like they'd last a long time). This also lets you play multiple games at the same time, whereas free-to-play players can only play one game at a time.
The whole thing is cute, has lovely art, and a fun mechanic that is really a far cry from other MMOs.
I think I'll be playing a lot of this over the next few weeks.