Wow, thanks for the detailed comment! Glad you enjoyed the game. As I said in other comments, the game is not polished and finished completely due to the lack of time, so pretty much all critiques are valid. But I'll also comment on some specifics you mentioned:
The left side of the room was indeed supposed to be cleared without the ghost xd. We made the second room hard intentionally because, well, lack of content otherwise lol. That would probably not be the balance in the final version of the game. Also, the ghost just has unintended interactions so you can basically skip 2 rooms with it (which I actually find pretty funny and interesting).
As for the boss, we wanted to make something different. So instead of you killing the boss directly, here the boss has stamina just like the player. And since the boss wants to stop you from progressing further, he uses his skills and thus uses stamina. Now when he expends all of his stamina, he can't do anything to you anymore and thus dies. So the main goal was to basically survive until he is out of stamina. You can however use your abilities still to help you. The explosion can do 2 damage (stamina) to him, and you can use the dash to dodge his attacks (especially in later phases). Of course, this system would be further developed and polished had we had the time to do it.
As for the "zero guidance" approach in the game, since we didn't have time to finish everything, we chose to have the most minimal UI possible. The entire UI is just your stamina bar and boss stamina bar. Ideally, there should be some help telling you how to interact with items when you first encounter interactable items and how to use your abilities when you unlock them. Also for the dash, yes, I should have coded it so that it doesn't interrupt unless you specifically press the opposite direction of the direction you are dashing, that was a mistake on my part but one which would later be easily fixed.
Also for the running out of stamina part, we did plan on having stamina refills throughout the levels as a sort of checkpoint, but since the levels were so small, in the end, we just added a respawn button lol, which sort of fixes this issue.
Once again, thanks for your nice comment, we really appreciate it!