Very nice short game, I wish there were more levels with more mechanics as each level progresses. And also, tip of advice, the reason the window is like that when you fullscreen is not because of a bug, but because many game engines do that. I personally use gamemaker and to fix that problem, I made the width and height of the game to the browser's size. You could look up a tutorial how to fix this, I'm sure there is one!

Besides that, this game was a nice little game :)

Amazing game, really fun to play! The dominos and balls were very entertaining to me. For level 7, it would have been better to at least have some kind of visual cue, to show that the domino is heavier (for example, make it bigger or a slightly different color), as it does feel slightly annoying when you wait for the entire chain to fall, but then stops at the final domino, but you can't tell it any different from the rest. Lovely game though, with great art and music.