The controls feel rather stiff. Especially the jumping controls. I found myself dying over and over due to an inability to run jump which was frustrating. Ultimately, this was the crippling flaw. During the boss fights I was basically spamming hoping I could kill it before it would kill me. The controls didn't feel fluid enough to allow me to properly dodge their attacks.
Honestly, after this I didn't really feel motivated to keep playing. I also found a particularly devastating glitch which I'll get to in a second. I feel all games should have a mute button (the music wasn't bad, but it got grading) and also I like to listen to my own music, especially when playing actions game like this.
The glitch I encountered allowed me to skip through the entire game. If you right click and keep hitting the "Play" button, you will continuously be warped through the warp points and basically skip over the entire level. I made it through half the game without killing any enemies in about 2 minutes performing this glitch.
Ultimately, some bug fixes need to occur (especially for the major glitches), a mute button for the music needs to be added, and the jump controls need to be more precise. Overall though, it wasn't bad. If it's updated and these problems are fixed, I'm sure the resulting product will be great!