Gaming sector functions like a giant factory and a huge industry. Investments in and required labor for the design of a game can be taken as an indicator of the importance of the sector. While designing their games, all companies working in this sector primarily focus on how the players feel, and thus, explore the ways to stimulate their interests in the game for a long period. One of the main strategies to increase user interest in a game appears to be the use of add-ons. Games enabling users to transfer their own created contents to the game in the form of add-ons seem to be the most successful in the sector. Accordingly, the main objectives of this study are to analyze how user-created contents affect players’ performance while playing the game and how they feel when using the content they created themselves. For the latter, a special eye-tracking system will be used in order to measure players’ respond periods during gaming. To this end, Mihaly Csikszentmihalyi’s “theory of flow”, which is considered to be a groundbreaking work in the field, and Jan o. Blom & Andrew F. Monk’s “theory of personalization” will constitute the theoretical background. When it comes to players’ perception of and engagement with the game, a survey will be conducted online, catering to a large group of players in addition to that which will be conducted with the sample group of said experiment. This will also allow me to compare the two data.