I think of the five dimensions as: 1. Horizontal within a board 2. Vertical within a board 3. Backwards and forwards along a timeline 4. Up and down across

I think of the five dimensions as: 1. Horizontal within a board 2. Vertical within a board 3. Backwards and forwards along a timeline 4. Up and down across timelines 5. The timeline of how the game actually evolves, building out the tree. This is a bit of a stretch, since you can't move pieces through it in the same way as the other four.