Cool little game!
In the beginning I had a ton of difficulty figuring out what to do. I waited for a long time staring at order screens of 0000 because I thought from time to time orders would pop up. After several tries and minutes I realised that orders of 0000 have to be pushed in. If others also face this issue, then one solution could be to remove 0 from the random options entirely? If the game is about getting items onto a tray and pushing it, then logically speaking, a 0 order goes against your desired gameplay loop.
But that aside it was quite fun. As mentioned in the other comment, a timer feature or a couple of other small challenge inducers would add to the enjoyment.
All the best for future work!