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Play to Earn is an evolution of Free-to-Play model - games remain free but offer players ownership on different items. This works by giving the user ownership of individual items in the game. Rare items can quickly increase in value due to high demand. The greater the number of players, the more income can be generated from rare items. Most of the games use ERC-721 tokens, a non-custodial [Sapien Wallet] and also supports them.