zenorogue

For an analogy: an Abelian group is a structure in which four axioms hold. A non-Abelian group is a structure in which three of these axioms hold, and the fourth does not. It is not a structure in which some random proper subset of axioms holds, because such a notion would be useless. While structures where specific subsets of axioms hold (non-Abelian groups, semigroups, monoids, etc.) are useful.

The hyperbolic paraboloid is not an isometric embedding of the hyperbolic plane H2 in Euclidean space E3, because it does not have constant negative Gaussian curvature.

In general it is impossible to have an isometric embedding of H2 in E3, although it is possible to have isometric embeddings of fragments of H2.

No, you are confusing geometry and topology here. Topology does not change when you stretch the space but changes when you cut/glue it. Geometry does not change when you cut/glue but changes when you stretch. So portals change the topology but the geometry is Euclidean (you get a Euclidean manifold). This are the meanings used by mathematicians working in these areas.

(The original meaning is of course about breaking 5th postulate while all the others hold, showing that it was possible was a celebrated result in mathematics, while it is trivial to break the postulates in some arbitrary way.)

Yeah, Jeff calls it "non-Cartesian". He changes the topology but the geometry is Euclidean. There are also lots of roguelikes doing other experiments with topology, tilings, dimensions (Verdagon 7DRLs, geometry episode of Roguelike Radio, etc.)

AppStore only accepts games compiled in a new version of XCode, and I have only a very old Mac on which it does not seem possible to install such a new version.

Google Play is not very friendly to small developers who do not want to share their home address (not their fault, it is some recently introduced EU law), but the Android version can be downloaded from itch.io

For Epic, I am using Heroic Games Launcher, I believe it is much better than the official Epic app.

There is a fascinating genre of games where space does not function as in does in our real world. Such games are celebrated, among others, for their mind-bending puzzles, psychedelic 3D visuals, and surreal exploration.

Sure, CDDA is a roguelike -- the word was supposed to mean primarily a specific way of controlling the character, introduced in Rogue. Everybody in the roguelike community calls it a roguelike.

"Stone Soup" refers to the Stone Soup folk story, where people contribute their supplies to make a great soup for everyone (it is developed by many people who contribute to the open-source project started by Linley Henzell as Linley's Dungeon Crawl).

Still a better name than NetHack (which is not a game about hacking networks... "Net" just refers to collaboration over net to improve the game Hack). There is also BrogueCE ("Brogue Community Edition").

But how much have you played it?

When I started working on HyperRogue, I expected it to be a "gimmick or tech demo" as you say. But after implementing the basic roguelike gameplay, it felt surprisingly good, better than what I had actually planned. So released it, and other people liked it too.

So it is not surprising that people expect it to be a gimmick (given that I did expect that hyperbolic geometry would make basic roguelike gameplay feel better myself). Some people do not get it on their first try, but love it on their second try.

Might depend on the interpretation of "roguelike" -- Rogue combined single-character adventure with grid tactics, so to many people, "roguelike" means single-character grid tactics, usually with some other less unique features (such as randomness), just like it did in the 80s. This was also the most important roguelike feature for the design of HyperRogue. While more commonly "roguelike" is used for marketing anything that takes whatever inspiration from a game marketed as roguelike. In the roguelike communities, mentioning The Binding of Isaac (in a way suggesting that roguelike means a game like it) happens regularly and yields very negative reactions, because it is not tactical and thus not interesting to the community. Similar for the other ones you mention.

Still, there are many very polished roguelikes on Steam (Dungeons of Dredmor, Crown Trick, Sproggiwood, Moonring, etc.).