The Concentration Grid app is based on the mental focus grid exercise. Mental focus grids have long been used as a tool by coaches and sports performance/psychology professionals to assess and improve performance of their athletes. The objective of the grid exercise is to select in sequence each of the numbers (randomly arranged and presented) in the grid. Performance is timed. The challenge is to complete the grid as quickly as possible. The exercise calls for focus and concentration. The grid exercise has been a long-time favorite of many baseball/softball coaches and players (typically using paper sheets, a pen and a stopwatch). Coaches/sports performance staff and athletes now can do their mental skills training work (and save paper) by using the Concentration Grid app on their mobile device. The Concentration Grid app is intended to provide competitive challenge and a fun/entertaining experience that is simple and straightforward ... like the printed paper grid exercise ...