Several varieties of trees compete to grow and spread their seeds in the sunlight of this small, but fertile, forest. As each tree grows its leaves are touched by the sun’s rays, collecting Light Points and casting shadows on the surrounding smaller trees. When a tree reaches the end of its life cycle, players win points proportional to the richness of the soil the tree was rooted in. Within Photosynthesis, players take turns sowing trees onto a board. After each turn, the sun rotates one corner around the board and shines rays in a linear manner across the board. The trees you have grown score points if the sun's rays have landed on them. However, taller trees may potentially block out rays of the sun from hitting the shorter trees behind it. Using light points, players take your trees through their life cycles, from seedlings to fully grown. Then, players collect Scoring Tokens with points proportional to the richness of the soil on which the trees grew. The player with the most points at the end of three solar revolutions is the winner.