High scores
Organize competitions with the puzzles and memo games and to encourage participants to do their best and outdo others with high scores.
With the leaderboard, you also ensure continued motivation and a real championship feeling. This is because the high scores of the participants are recorded over the entire duration of the calendar. This way, not only you as the organizer can keep an eye on your users, but they can also keep an eye on their competitors.
Of course, you can then export all participant data as an Excel list and notify the most successful players.