Imperial Miners

You are digging a mine, one card at a time, and it grows downward from the surface. Every card you add activates itself and every card above it, so the deeper you build, the longer your chain reactions run. The cards come from six factions of the Imperial Settlers world, and mixing them is where the clever combos live. Along the way you also push tracks and react to events, while everyone picks actions at the same time. This is a stand-alone game by Tim Armstrong, light on rules but rich in satisfying engine-building, for 1 to 5 players in about an hour. It also works well as a solo puzzle.