Ads ads ads. Increasing long video ads with oddly inaccurate close buttons. F2P, P2W with cost curves in later levels that make it a tedious chore to progress by actually playing the game. I quit when it became more fun (more fun meaning "less awful") to watch ads for in game currency than to play the same level 5 more times. And then there's the fire gameplay and levels. Careful skilled play vs just holding the accelerate button down has no significant effect on the outcome.