StreetSchool makes maths something kids want to do. Instead of dry drills, it turns learning into kingdoms, quests, missions, comics, and music, so a normal kid can have fun while the maths sneaks in.
I built the mobile app. I focused on making it work well on cheaper phones and shaky networks, because that is what most kids actually have, and I kept it simple enough for a child to use on their own.
Building it taught me that the hardest part of education tech is not the lessons. It is making a kid want to come back tomorrow. The quests, comics, and music are there to earn that.