Thanks for releasing this game! I love the cartoony character pixel art style, it's very slick and consistent, and the design of the main character is cool - that hairstyle, man.
The way you get a jump boost off the "coins" is cute, never seen that before and I quite like it. Once they're gone, they're gone, so you are encouraged to make the most use of them and think ahead. Please keep this.
Main things I would want to address first are the level design and the camera. First thing that stuck out is the camera following you up & down exactly whenever you jump, it's jarring and makes it hard to avoid enemies. Usually you don't scroll vertically until the player lands at a new height from where they jumped. See how other games handle this.
Following on from that, the vertical design of the levels makes for constant leaps of faith - once you get high up, you have no idea what you're going to land on when you fall. Maybe once in a while this is ok, for super secret areas up above, but I think that happens so often in this game because of the jump boost pickups. Try to make it so you can always see a lower platform below you from the one you're standing on.
Also am I supposed to be picking up as many gold pickups as possible? The sheer number of them make this feel like a chore and I ended up forgoing them and just aiming for progression, only using the pickups to boost my jump.
The screenshots seem to suggest a lot of gameplay is up ahead! But the instant death and returning to the start of the level, coupled with the leaps of faith and super fast jumpy scrolly movement, meant that I felt like this was going to boil down to a lot of level layout memorisation which was going to get tedious! So I never made it past the first level.
Hope the feedback helps, with some level tweaking and camera tweaking, it would be interesting to see how it plays next.