It's like an RTS tower defense game, but you build the fortress you are defending piece by piece out of LEGO-esque prefab blocks that stack together in specific ways. I spent an hour and a half on the 2nd tutorial trying to get my wall just perfect, only to realize it's much simpler than I thought.

Almost any wall, no matter how silly looking, will do the job because the game determines a wall's strength by how tall it is, not how architecturally sound it is. Mix that with units whose strengths lie with being at specific height ranges, and you've got a fun lil gameplay loop.