The top down view reminded me of gauntlet! I'm behind merlin4's comments - some more visual feedback on hitting enemies / enemies pushed back on hit + player slides forward when swinging the hammer would give the combat more momentum.
I like the fact there are multiple enemy types to spice things a bit. Have you thought of adding more hammers to choose from for the player? some with longer reach, slower but more powerful etc. I think it'd add some more variety to the combat.