Nice work for a start. There are a certain amount of bugs, like most of the hearts not diappearing after you take them, the hearts and ennemies not reappearing after you die, the beginning of the game after you spawn that is really laggy and I once died and got teleported out of the level and somehow managed to get back on track bie respawning randomly. But it doesn't prevent the game to be played or finished so that's OK.
The wall jump is quite tricky to perform and as a result is quite slow which makes it a bit annoying in the long run but it works quite well. I did not get that the white ground was dangerous and jumped in it thinking that it might be jumpy or something, terrible mistake I made ^^ it could be clearer that it is dangerous.
Regarding your thematic mechanic, I did not see a great difference between full life and almost dead and just preferred to get as much life as I could to survive. I noticed a slight difference in speed but nothing more than that so I don't think you're intended purpose with it works for now. I felt more that the less life I had, the better it felt but the more dangerous it was. But the idea is cool and could work with some adjustments I suppose.
Overall, this is a quite nice first game, especially since you were on your own. Good job, and keep on going!

Hey!
This is a decent game. Even if I stumbled upon a few bugs (the teleportation out of bound mentioned by @yacuzi), I had a good time playing it.
In my opinion, the wall jump mechanic is a bit broken, you should freeze the player as soon as he touches the wall and gradually increase gravity over time.
Anyway, I keep in mind that you did that under three days, so good job on your submission.

Thanks for the feedback so far guys, yeah I was pretty rushed for time due to having to work full-time over the weekend and fit the game jam around that, and ended up rushing the level out. Hearts were meant to destroy themselves upon touch but I didn't add the touch sfx on the duplicates which prevented the pickup effect happening for some reason. As for visuals, my artist unfortunately had some big life problems come up, which had to take prirotiy over the jam :(. Cheers for the advice though, I'll work on it asap <3