So I gave it a try, and I really love the concept! But damn is it easy to die. While I understand that this is a demo, and you mentioned in another comment that the final version will have a much easier difficulty curve, I still didn't feel like a lot of the deaths were my fault and I think that has a lot to do with the control. I love the idea of a one button game, but it almost seems like an artificial restriction that's hurting the overall feel, trying to attack but being forced to jump and run to do so makes some of the arenas feel extremely small and having three enemies in back-swing tailing you means if you stop for a moment to attack you get obliterated. Compounding that is the fact that you only have a limited number of playable characters, and I don't even want to know what happens when you run out. I think this concept could go a long way, but as the demo stands, I felt as if I were being punished for deaths that were unavoidable.
Thanks for posting your play-through! I actually meant to ask you to take a look at this game, since you also reviewed our GGJ game "Static Breach" earlier - but you got ahead of me!
Watching you play the pirate level did make me cringe a couple of times. We wanted to show one of the later levels in the game and while our testers had no problem beating the level, it can obviously be quite daunting for a new player who's still trying to get a hang of the controls. By the time you would normally reach this level you'd have some stronger characters available too. So maybe I'll nerf the pirates a bit for the demo.
I'd still love to see you give arena a shot with a friend some time.