Wow, the game is really hard! And weirdly really really fun (didn't think that a game where you just walk and rewind tapes would be so fun)! For some reason though I couldn't hear sounds (though I saw you added some from the credits (:.) and I think they would have made it much better. Anyways, the main thing I think you should do is explain a bit more - I didn't understand at first that you could switch between a rewound tape and a non-rewound tape in the rewinding machine to save time. But even with that trick, it was really really hard. Maybe you could make a normal mode where there aren't customers with 3 tapes, and a hard mode with those customers. But it just seems impossible to survive for long with the 3 tape customers. I don't know, think about it.
Another small thing is telegraphing whether the tape will be ready soon. That will allow for more strategising.
I think you should try to add more depth. Maybe increase the amount of customers and add another rewind machine. It will make the game a lot more frantic and will add to the strategising you can get by telegraphing the end of the rewinding. That's just an idea that I don't think will take a lot of time to implement but will add so much more to the game, but it might be a bad idea. The main thing is - I think you should focus on adding some more depth and planning to the game, and if you can also make it quicker. Maybe make the top speed a bit higher?