Bugs: Nothing really
Strengths: The character is easy to move, I like that the black stuff (not sure what it is) tracks the player and the player flashes when hit
Weaknesses: There is no goal/purpose right now or way to defend yourself against the black stuff. The background is quite plain and it's not clear what you're meant to do e.g. explore rooms, fight different bosses, etc
Changes or Improvements: Could add a health bar and more details