This game is interesting but I think feels more like a test build to a game rather than a full game in and of itself. As far as I saw it, there were three major issues: (1) the poor utilization of the collection mechanic in the level design, (2) simplistic and lacking level design that did not promote any thought and instead promoted blazing through the levels without a care, (3) and the sudden switch to a (rather poor) shoot em up.
1. The collection mechanic is the main reason I feel like this game is a test bed rather than a full game in and of itself. The collectibles are left in a straight, linear fashion throughout the levels (with the exception of level 9) and aren't used in order to enhance the levels and give more thought to the player as they travel through them. While the collectibles should be left in a linear fashion in the first level or two in order for the player to get the idea, later levels should have the collectibles in branch paths, thus encouraging/forcing exploration of the level and allowing for more challenging and thoughtful level design.
2. The level design itself wasn't anything too new or too interesting. All of the levels (even level 9, which I mentioned earlier) are extremely linear and are all composed of the very basic "jump to the next platform, avoid the hazards" that are essential for a platform game to function but need to have a different spin in order to remain entertaining. There were plenty of avenues to put a spin on it (in the form of the collectibles or even the disappearing/moving blocks) but these are mostly just used to add flavor to levels in place of substance.
3. The random change to a shoot em up in the last two levels greatly bothered me. While the level design was rather boring, it was mostly regarding the speed of how it played and how stiff it felt to control, especially compared to the rather tight and good feeling controls of the platformer levels. Shoot em up style levels need to be fast, especially in regard to vertical movement. If not, everything will feel slow and often or not your player will get frustrated at the level design rather than their own mistakes, as it's difficult to judge whether or not you might make it around an obstacle when your ship is moving so slowly.
Besides the major issues, the game did have a nice feel to it and the speed of the platforming felt very good to control, and kudos to you for making it like that. You could easily use the code you used for the movement again in another game and I'm confident as long as you worked on the level design you could have a really good platformer on your hands.