Thanks for a rendition of Box Sorting Simulator 2021. I really liked the background and movement of boxes (and conveyor stripes!). Sounds were really well picked. Also thanks for a detailed ingame help though noting there one needs to fill a sorting area with 10 boxes before any of its points are added to the main score would be helpful ‒ I got confused my final score is 0 even though I sorted some boxes (but not finished any 10-slice of them).
Mouse cursor was not showing for me but adding needs_cursor? method to the code solved it. I guess some of your settings outside of this game make it you have a default cursor even without needs_cursor? in game code.
I once managed to put a box on a stopped conveyor where that box did not start moving once the conveyor was activated again. As that clogged the loading area, that attempt was doomed. It seemed to me this happened when I managed to load box on conveyor just as I was billed 50 points for another box reaching the end of the conveyor. I was not able to reproduce the bug, though.
Is the speed of new boxes actually increasing? I played for several minutes once, reaching score of 10555. Chaos (beside the initial pile of boxes) seemed to be coming self-caused when I managed to misclick on a colour I was trying to process in given batch.