Changers is a mobile-health application providing wellness programs for citizens, employees, and customers developed Blacksquared. Its CO2 fit app motivates in playful competitions to switch from car to bike, walk more often, use public transit, and take part in healthy and climate-friendly activities. The app tracks the participation, calculates the CO2 balance, and rewards eco-friendly behavior with a CO2 token, which a user can redeem for tree plantings, donations, or vouchers from an employer, city administration, or merchants.