I've finished the demo and killed the boss on my first run. I died once in the water level.
About the boss, it's good enough for a first boss, i think, but can be improved.
- Instead of several worms, i'd like just one big worm.
- At first, the worm moves only once across the screen, each time from a different border. Only the head (half on its lenght, maybe) is punchable. After a few hits, it comes into second form.
- Second "form", same, but instead of going out of the screen it turns over to be "double lenght". It can be in line, cross, up, left, right... what ever, but it's longer. Only the head is punchable (so 1/4 of its lenght).
- Last "form", same, but three lenghts, and again, only the head is punchable (so 1/6 of it's body).
- I'd suggest to make the border of the screen blinking according to where the worm will come, then move the worms out, so i can replace myself if needed.
Just my opinion.