I could offer my experiences on the level requirements. To me, everything seems well balanced through size 6. When I reach size 7, the next level is a bit on the hard side but not too bad. (I did better there in the video than I usually do.) When I reach size 8, the next level is extra easy. Then when I reach size 9 the next level takes an enormous amount of stuff and I find very few flashing objects. That's as far as I've gotten.