Fun little game! Some feedback, as requested:
The game opens fullscreen, but the playable levels aren't scaled to fullscreen. I can also see the background is not infinite :D
Throwing a heart is always at full force, regardless of how long or short the pointy line or me holding spacebar is.
The game is very forgiving for mistakes in most of the puzzles, with the hearts sometimes starting to roll towards the target spontaneously. Not sure if intended, but it's a nice touch.
I dislike invisible walls, it's just restart bait. Would rather have that information up front.
While the levels are varied in style, they don't really evolve in mechanics until later in the game. The keys mechanic is interesting, but with the current level design and with infinite restarts it doesn't matter much as you only need to hit it once, and then you have two more attempts to hit the soulmate. Same with the jumpers. What would be interesting is having a few levels where you have to make 3-4 perfect-ish shots in a row in order to beat it, that would increase the challenge a bit. Or perhaps having to time the jumpers, to use them for an extra bump rather than avoid ing them. But of course, this would make the game less cozy so that's a tradeoff :D
I dislike having to manually select the next level after beating one. Makes me have to remember what I was playing :D would rather it just automatically go to the next one, and perhaps also mark the completed ones in the level select menu.
Overall it's pretty enjoyable to quickly play through. Good job!