Abstract
In this work, we analyze the aspects of user reactions during their work with a mobile phone. We tried to find the most crucial positions within the mobile screen, which provide essential information and stimulus. One of the main factors is to know which part of the screen is the first interest of the user and which part the user reacts to the fastest. Sixty-four persons participated in an experiment. We used the gamification approach to motivate users for the best results and created a game. Users competed with each other during the game, and they tried to react to the new point of the screen as soon as possible. The experiment showed that about a quarter of the screen below the centre was an area where users react the fastest. There were interesting differences between men and women and signs of background impact.