I finally got the Epson RC-20 computer watch that were released in Japan in 1984. An amazing feature of these watches is the ability to write applications for them, and this task is simplified by the fact that they uses a Z80-compatible processor. Of course, I took this opportunity and as an entertainment wrote for them a clone of Google T-Rex game. Video review of these watches can be found here The author of this video shared with me a developer manual, without it, I certainly could not do anything. Sources available on GitHub - Music plays not on the watch :)
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