Works perfectly, liked it a lot and it made me check out the music of Flashburn, which alone would be worth 5 stars. Record hunting was a lot of fun.
If you want to expand on this game, adding some other characters would be fun.
- A slower charged but strongercrossbow. Introduce "hearts of stone" or "frozen hearts" that you have to hit several times with the bow, but only need one shot with the cross bow.
- A gun or rifle that is fast and has no gravity penalty, but relies on ammo that you have to shoot for (flies down alongside hearts and also has negative ammo that eats away your current ammo if you hit it)
- A ventilator gun. Can only destroy hearts indirectly by collisions or blowing them towards some needles you may put on the level in advance, opening up tons of strategies to rake up combos
Different planets with different backgrounds and different gravity values. Also wind would be a nice factor, especially if you could change the wind's speed or direction hitting certain targets or power ups.
Regarding the power ups:
Nice variety, but I felt the game would be even better if there was a mode where you picked up power capsules instead of power ups and could activate them similar to the Gradius weapon upgrade system making things less randomized so you could prepare big combos and enable your own playstyle instead of only reacting to whatever comes up.
Another mode could be a room with fitted buttons that make a power up drop (or outright enable that status), letting you choose that way.
You could even make a campaign mode where experience could be added to skills (like dropping certain power ups more often or getting more impact or duration out of them), including being matched up against a bot player that tries to hit more hearts than you.
I honestly believe this here could perform the basis of a variantful and multilayered game with polishing and deeper gameplay. I'd love to see you come back to this (or someone else taking up those ideas for a sequel in spirits).
Anyway, some well-deserved 5 stars for you!