Video from channel of an owner and restoration hobbyist from Poland who owns and runs a working (as far as age and quality of socialist era components allows it) unit of that computer. Mera-400 is a descendant of legendary K-202 architecture designed by Jacek Karpiński (Polish computer systems engineer known for analog and digital computers designs including his 1964 variant of Perceptron - early neural network type of computer).
More detailed article on Jacek Karpiński is available at English language wikipedia.
Mera-400 was notable for running CROOK operating system that was an OS influenced by UNIX.
Video with subtitles, you can use auto-translate to English: https://www.youtube.com/watch?v=H7gh1PEqVak
