You get a boomerang and no sword. Throwing it sends it out and brings it back along a path you only partly chose, so hitting something means thinking about where you will be standing when it returns rather than where the enemy is now. Hearts across the top, coins along the way, and rooms that open once they are clear.
It was built to fit inside thirteen kilobytes and it uses the space on the parts that matter: the throw feels right, the enemies telegraph, and the rooms are laid out by someone who knew you would be walking backwards through most of them. Twenty minutes, one sitting, and a real ending.