A very solid game, with potential for long game sessions.
I liked the gameplay and the art. Less so the music (good but too repetitive)
The critique I'll make is regarding user feedback (if you can call it that way). For the first ten clients or so, I was sure I had to go to give the cassette to them. It led to me frantically pressing E and F around them until the bubble went blue (which of course wasn't my doing but I had no idea...). A sound effect or a graphical feedback letting me know that pressing the buttons didn't do anything would have helped me :)
Good job on your entry!