Hi! We are glad you liked the game, and yep, we are aware that perhaps we made it too difficult, so pat yourself in the back because even reaching the boss is an achievement!
I am not sure how you lost your progress (is it possible that you deleted your browser's local data at some point?), but if you want to be sure you won't loss your progress you can download the executable version for your OS.
We are currently working on a sequel! and we post some updates on @MDProjects_dev on twitter every once in a while.