A free online programme from Hack Club, the teen coding nonprofit, running until 31 October. You build any open-source technical project (a website, game, app or hardware), log your hours and publish it; other teens rate it, and the stardust you earn buys prizes such as a Raspberry Pi or a 3D printer. Logging 30 hours of verified work earns a certificate of achievement. No experience is needed, and there are no judges or winners.