What are the blue bullets?
Right below the life there are blue bullets. What are those? How can I use them using a Xbox joystick?
Solution 1:
Those are Blanks. When activated, they give the player a small breathing room by clearing all enemy shots in the room and pushing enemies away from the player. Blanks can also break open paths to secret rooms if any exist in the same room. Activate Blanks by pressing Q.
By default there's no way to use a Blank with an Xbox controller, as seen here.