Designing and developing games for learning is a difficult endeavor. Educational game designers must not only make an engaging and motivating game, but must also ensure that learning takes place as a result of gameplay. Educational researchers have sought to define design principles in order to lessen the difficulty involved with game design. In spite of these efforts, there is still a paucity of empirical research in support of significant direct learning gains that result from time spent in a game environment. This study investigated the effectiveness of a design and development approach centered on playtesting, with the purpose of ensuring the proper intrinsic integration of multiplication properties, concepts, and strategies within the game's mechanics.