The game is really fun and addictive, levels are quite creating and done nearly masterfully...
You truly have to master all of the mechanics to finish the game...
Apart from that, the music is glorious. It's just awesome, fits well to the entire idea of the game and even the short plot, although the shitty loop in menu and boss fight is.. well... Shitty, you didn't even bother to change it for the boss fight... That's why its 4 stars instead of 5.
The underground music though is truly a masterpiece, fits so well. Well done.
Other than that, some hitboxes are quite badly done, in some places when slamming to the ground with "D", even though you're nowhere near spikes, you will touch the nevertheless, however it happens quite rarely and can be countered.
And now the worst part of the game: Score system. It's just fucked up.
You should completely scrap it and create some kind of a time-score system, therefore the better you are at the game, the faster you'll complete all of the levels and the higher score you will get.
I ended up getting multiple points for the same level, even though I got all of the points there already.
When replaying a level, it shows you your previous score, but does not even mentions your current one, and the previous score can sometimes be misleading as it shows the previous score from other levels. Odd. That made me give up on trying to get the biggest score.
The game holds even more potential though, if you'd choose to extend the plot and add entire chapters in any of the next updates, you could even include something resembling liquid physics, would be quite fun, underwater levels.
Overall the game deserves a fine 5 star rating, yet just because of the score system, shitty menu loop sound and the same loop in the boss fight, I can only fairly rate it at 4 stars.
I have also anticipated a second boss fight... I have been disappointed though...