Comparing Game-Based Reward Systems to Support Children's Engagement:

Inclusion Criteria: Children aged 9-12 years Regular smartphone use (at least 4 days per week) Has access to a smartphone throughout most of the day Brings a smartphone to school Owns a personal smartphone with a touchscreen Owns a smartphone with Android operating system (version 9 or higher) Has access to mobile internet on their device Is allowed to use a smartphone at school during breaks (e.g., lunch or longer breaks) for questionnaire completion and to wear a smartwatch Native Czech speaker Exclusion Criteria: Does not meet one or more of the inclusion criteria Has a sibling already enrolled in the study