Next! Fitness - A.I. powered gym
Crosswords Arena - Word game, multiplayer and computer players
Dualnback.works - Dual N-back is a specific brain training exercise, that's been shown by research - it might improve fluid intelligence.
Tanglet - Tanglet is a single player word finding game based on Boggle.
Praxis - Apprenticeship program and career accelerator
Quackle - Open-source word game similar to Scrabble. Features a board editor, analysis tools, and artificial intelligence that rivals the best players in the world!