The idea of not having bullets to fire, but a grappling hook to drain the enemies health is really dope.
Got a little frustrated at first because as I was trying to read the tutorial it kept killing me. Could perhaps do with a pause and confirm tutorial, but once I got the concept, it was great fun.
Definitely very tech-demoish as you stated, but I think if this was fleshed out a bit, polished up and prettified this could become a great little game with a new and enjoyable concept.