The game is designed as a series of conversations between two people, one asks questions and the other responds. The responses almost always include a mini game where the player solves a simple task to understand the concept.
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To promote the game to a higher extent and make it more likely to become popular, I'd add a game inside your app with weekly winners. The game would only become unlocked if you pass 1/2 of the courses, but only practice mode. If you want to win the prizes, you have to finish all the courses beforehand.
Say there's a trading game in there and you have to guess if the price of BTC is going to fall or rise within the next 30 minutes. If you get it right, you get a point. The more you get right, the more points you earn. If you miss a prediction, 2 points are deducted OR your score resets. The winner at the end of the week (with the highest points) would be rewarded a little prize ($10?).
I know there's a quite large number of people willing to spend their time on apps to earn even a few cents. If you're going to make a little competition, more will be interested to join.
Kids vs adults shouldn't be a concern. Kids learning about BTC and financial freedom is a great idea. They should grow up with decentralization in mind imo. Fuck the state-controlled worthless paper money. Adults who are interested to learn more about BTC (or, if the idea above turns into reality, even those interested in trading only) will download your app if the design is user-friendly and fun enough.
Best of luck with the development, make sure you leave some updates here every now and then!