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Sapiens: Mountains is a set of eight landscape tiles for Sapiens with one-half of each tile being one of the eight normal landscape tiles and the other half of each tile being a mountain, which is what surrounds the valley on each individual's playing board.
During set-up, place these eight mountain tiles next to the scoreboard. During play, instead of placing a tile from your personal pool onto your player board, you can place one of these mountain tiles, with the mountain half lying outside the normal play area and the other half matching an adjacent tile (and scoring food points and a bonus) like usual; if you cover a cave with the mountain half of the tile, you earn no shelter points for this placement.
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Sapiens: Double Tile contains a set of 8 double-sided tiles that show each of the 8 scenes in the base game on both ends of the tile.
Setup - Before the beginning of the game, shuffle the 8 double tiles with the base tiles. Then, during setup, remove 8 tiles in addition to the normal number removed (so 20 tiles for 2 players, 26 for 3 players, and 14 for 4 players).
On Your Turn - During the game, treat double tiles just like normal tiles. Each offers the same scene twice.
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Double tiles doesn't make the game any harder; however, the mountain tiles add in an additional layer of complexity (and more decision making).