Choo Choo Zoo needs to get harder at higher levels
Playing the game the first couple of times, when unsure of exactly what to do, isn't so bad. But the combinatorial invariants involved aren't hard to figure out. It adds more animals as you get higher level, but only up to level 10. And then it repeats level 10. And repeats it again. And again. And again.
The problem with this is that level 10 is usually pretty easy. Occasionally it's a bit of a nuisance if you have to just survive a while, waiting for an impossible map to change so that you can dig something out of a corner. But "takes several minutes" is not the same thing as "is hard to beat".
Now, level 10 being easy would be no problem if it kept adding animals until you fail. But it doesn't. So the third or fourth time I played, I got to level 30. I didn't play Choo Choo Zoo for a while after that because it took too long.
Finally today, I tried it again. Big mistake. It took over an hour and a half to finally fail on a misclick at level 63. That's way too long for a minigame.
A game shouldn't rely mainly on players intentionally failing after a while to get the game to end. There's a simple fix for this, really: keep adding animals. 10 animals is fine for level 10. Make it 11 animals for level 11, 12 for level 12, and so forth. If you need to eventually use two copies of the same animal to save on art costs, that's fine. Do it. Just make the game end in a reasonable amount of time, and make the reason it ends be that it got too hard for the player.
This would probably require wiping the high score list, to prevent the existing scores from being unassailable if it is no longer possible to reach high level numbers. That's fine. Do it. The game will be better for it in the long run, and it's better to fix it now than later.
I'm not sure if other games have the same "the game takes forever if you're good at it" problem, but if so, that should be fixed, too.