Internet Archive has a playable online portal for what you would be buying here from GOG, the 1988 US MS-DOS edition of Echelon developed and published by Access Software. I think it's well worth it to have the game running on your local computer --it's just a much better experience-- but this would be a chance for folks to kick the tires around first if they're on the fence about buying.

https://archive.org/details/msdos_Echelon_1988

And here you can try out the prior 1987 edition for the Commodore 64:

https://archive.org/details/Echelon_1987_Access_Software_Side_A

I picked this game up for both the C64 and PC in their boxed editions "back in the day", and still have them today! It was one of my all-time favorite games -- for the C64, especially. So I was very excited to see it show up here on GOG. It was ahead of its time in many ways.

Cheers!

-mwirkk