Thanks for the comments guys!
This is what I'm going to add to the game:
- Restart button to the both defeat and victory screens
- Simple sound effects (bfxr ftw!)
These are small changes and I hope it's not against the rules of the challenge.
I doubt I'll be able to squeeze a tiny tutorial into it though, but maybe an overlay with labels like "Action points", "Your health" etc in the beginning of the game will be enough?