I like the concept of fighting the scary monster ghosts of the enemies defeated. Great sprites!
The game is a bit difficult to play on "normal" though, as the enemies have quite a long range and run away pretty fast, so there's little chance to hit them while they quickly go down through the player's HP.
The final boss was funny. XD
Oh and the game attacks felt a bit unresponsive, like there was too much of a delay between the input and the actual attack motion. The game also "queued" my attack button spamming and the character kept attacking while I was trying to "ghost". If you can fix that, it would make the game more fluid and fun to play!
Great job!