Cool game, though dashes immediately ending if you graze a wall (including with movement keys while dashing away from it) got very frustrating and caused me quite a few deaths. Maybe consider having dashes either bounce off or slide along walls rather than immediately ending? The sudden lack of invincibility is very jarring when you get used to the dash duration. I also agree with arijun that it may be worth cheating a little in the player's favour with regards to the boss fight hitboxes; perhaps allowing a few frames before actually killing the player?
147 days ago(+1)
I find that the boss issue is mainly with the tip of the boss being able to move at relatively high speeds, which can kill the player early (I was generally finding that I was dashing a couple of frames late when I died to trying to ram through the boss). Honestly the bosses are probably fair as-is, but slightly shrinking the box on the tip (or adding an extremely short timer - 5f or less) would lead to fewer feel-bad moments for the player when they dash a frame or two too late.