I did what you suggested and dropped down the left side to play through the whole game. I like the use of 3D assets from a side scrolling perspective as it gives a lot of natural depth. Also, the boss's behavior during the fight is well done.
I suppose the criticism I have is that there don't seem to be checkpoints during the platforming section, as I keep respawning at the boss room. This makes that section a little difficult to play through. Also, the hit stun for the player is a little bit long, especially because you can't attack during the stun window.