Pay to win. Lives regenerate quickly but that's not enough to progress in the game. They don't have voluntary ads so there's no way to earn in-game currency other than beating a level within a certain timeframe. And there's no way to buy boosters other than in-game currency which are necessary for some of the levels very early on. This means you get stuck very quickly unless you buy their currency. Definitely a pay to win game. Uninstalling. Going to check out other options.