The concept is very interesting and I feel like there is definitely potential with this idea as a game. The gameplay is certainly unique and I did have a laugh while playing! It's quite difficult too, got a score of 21/25 as my best attempt, and I am really curious if a perfect 25/25 is even possible. For some criticism, I think the force of the box being shot out is too great, and making any meaningful stacking quite impossible. I ended up holding one larger box on the right end of the conveyor belt and hoped for the best. It would be nice if both the shooting force and the speed of the conveyor belt were to be lowered a bit, and hopefully, that would make stacking more viable.
Anyway, this is a nice attempt, and I hope you continue making games! Keep up the good work!