This document discusses how mobile app and game developers can improve their products by 25-40% through playtesting, which involves testing a product with target users early in the development process to gather feedback. Playtesting for only 5% of a product's budget can significantly increase its quality before release. The document outlines 10 best practices for effective playtesting, such as clearly identifying goals and metrics, observing users, and applying feedback iteratively. By addressing issues early, playtesting can help developers launch higher quality products faster and with fewer revisions than developing in an "information vacuum" without user input.