Not a bad attempt at a game. That said I have several remarks:
There is no pause state, and no in-game instructions as to how to control the character. Dying exits to desktop. The controls themselves feel a bit floaty. I would tighten them up. Holding the jump key pressed will make the character keep jumping whenever they reach the ground again.
Regarding combat: Keeping the attack button pressed after doing a dash will make the character do a regular attack when the dash ends. The skulls exploding is fine and could even make a fun game mechanic, but they are so slow that waiting for their explosion to go away is a complete pace killer at the speed they currently have. The damage knockback is not very good and it's easy to get stunlocked with how unresponsive the character becomes. This becomes an even bigger problem when certain room transitions spawn you on top of an enemy, including the boss.
Regarding the presentation: the music is nice but very short and quickly becomes jarring after it repeats over and over. The main character appears to have a significant black outline that gets completely lost against the background and only the white and red parts are visible.
The layout of the map was decent.
Got to the boss, got stunlocked to death and thrown to desktop.