PuzzMoney

This is a tiny puzzle that grows on you.
It’s the kind of game that embosses the rules on your brain within 5 seconds, but then compels you to spend the next 10 minutes playing.
Swipe the same money to exchange.
Money you tap first is exchange.
Money is available in Japanese yen, U.S. dollar, Euro, and Renminbi.
Moneys falling at regular intervals.
If stacked up to the ceiling, Game Over.
Can you make $100?
It's a unbelievable!