Spirit Island is a very heavy cooperative game. You play as ancient spirits defending an island from colonists. The invaders operate on a predictable system that you can plan around. Your powers grow stronger as the game progresses. It requires deep analysis and communication. You cannot just coast along. Every turn involves a lot of math and spatial reasoning. The complexity can be overwhelming for casual players. It scales beautifully and is highly regarded for solo play. A rewarding challenge for a dedicated group.