I'm glad you enjoyed it.
The boss needs more iteration to get the timing and difficulty right. It's a lot easier to defeat the boss with projectile attacks compared to melee attacks. Maybe that's what you are missing? I wanted to add a room that required the player to shoot projectiles and destroy targets before a door would unlock (so the player knows about the X button) but didn't have the time to code it.
I leaned towards a slightly more difficult boss over a very easy boss. I guess I got too used to the boss when deciding it had 6 health points.