Numble - It's like Wordle for Math equations.
DragonBox Numbers - Teach kids about numbers with an easy and fun game
Guriddo - Guriddo (グリッド, Japanese for grid) is a free and competitive number puzzle app with daily challenges.
Wikids - An encyclopedia that talks to your kids
BioBase - Measure and manage your stress
Four Seconds - A timer and a simple rule: stop it at exactly four seconds.