Cool little game. I have a couple of issues I want to point out:
1. The daisies feel more like a chore than a challenge to collect, since you're able to die after collecting them without losing them. This makes it so that you can just get them on your first run (for each checkpoint), die, and then do the easy route, which removes the intended challenge of getting them in the same run. A way around this would be to make it so that you only kept them if you reached the checkpoint in that same run, so that you need skill in order to collect them. There could be a counter showing the amount of collected daisies, so that the player knows how many they have.
2. The music is a bit tedious and repetitive. The main track doesn't loop, leaving an awkward silence while playing. The boss theme also doesn't fit the fight.
3. The animations feel very stiff.
4. The boss phases went on for too long, without any change in the attack pattern.
Even though I've only listed my issues with the game, I want to point out that I actually think it was quite a fun experience, specially for it only having been made in 3 days. I wish you good luck with your future projects.