It's actually the infinity symbol ♾️ It means you've received unlimited lives for a certain period of time. Once you activate it, there should be a little countdown clock accompanying the heart where it tells you how much longer you'll have unlimited lives for.
*May be worth noting: unlike some other games I've played before, the unlimited lives session does not reset your actual lives back to five when the unlimited period ends... so you come back to however many lives you had before activating.

It’s so you have a sense of winning before you’re challenged with the more difficult one that follows. Winning puzzles release dopamine in the brain that makes you feel good. The precursor of dopamine makes it easier to handle the harder game that may cause a loss. Without people would tend to just stop playing altogether.

I'm stuck on level 904 and cannot get past it. wtf.

Agreed. I'm about ready to uninstall this game app.

I'm on 253. Small board

Completely agree with you.

I’m on level 375 small board

Yup! Happened to me as well!

That's the only one I can't finish either. Not enough time to do it!

I need cheats for level 722

Cómo pasa el nivel 79 zen match

How do I find out the score / amount / whatever to pass daily challenge

I’m wondering the exact same thing!

My level is somewhere in the 100's and still a small board. Only reason I downloaded it was for the big one

Level 640 help

try the daily puzzles for a bigger board, but other than that - the ad is just a trick to get you to download it! i’m on level 154 and have yet to see a board that looks EVEN close to that!

I feel it’s the warm up before the match!