I was a little disappointed with Superliminal. Really short and I didn’t think the puzzles got very interesting. I was excited about the concept, but it really didn’t live up to my expectations. Glad you liked it, though! I think it was maybe just a little overhyped for me.
If you’re looking for other games in this style… The Turing Test was decent and short, and Lightmatter is pretty unknown and decent. They’re not as polished as Portal, obviously, but they’re both relatively short puzzle games. I think the puzzles in Turing Test were pretty straightforward. The Lightmatter puzzles were a bit more interesting, I think.