Novagen released the Atari ST version of Encounter in 1991.

The Atari ST and Amiga versions are pretty much identical in terms of look and feel. The Amiga version has a slightly wider display. The Atari ST version is well worth finding and playing though. It’s an interesting enhanced ‘tribute’ to the 1983 original.

Encounter versions on this website:
Commodore 64, Atari 800, Atari ST, Amiga.

More: Encounter on Wikipedia