This was a really interesting twist on the genre. It was fun and engaging. I feel like with more elements, this could be a really good game. It's definitely the start of something.
I didn't mind that the enemy moves in real time and so absurdly fast! But, I feel the player character should keep moving when w/a/s/d are pressed. I was frantically key mashing at times. Did you try out having them move on turns? Perhaps try using multiple enemies?
Also, the game could have done with some background music, but that's a minor issue.