Actually it is poorly documented. Controls, mechanic, the gameplay - it should be shortly explained, at least.
Yes you're right I just put quickly what I had done on the arcade haha. I put a new version on the arcade, where I added a temporary menu with a Help screen which explains quickly how to play.
I finished to do the first 10 levels (I need to twitch a bit the difficulty for 6-7-8-9 I think) and the tenth level is a bonus stage. Now I just need to do the boss for level 20 and it's almost over