Otter, the Online Table Top Environment Renderer, is an online game system.
But it is not like most online game systems. It does not know (nor does it need to know) the rules of the game you are playing. Instead, it lets you and your friends play with common tabletop/boardgame elements such as hands of cards, boards, and so on.
So it's something like a "tabletop simulator" (but it does not have any 3D, or a physics engine, or anything like that).
This means that with Otter:
Supporting a new game, that Otter doesn't know about yet, would usually not involve writing or modifying any computer programs.
If Otter already has the necessary game elements (cards, say) all you need to do is write a spec file saying what should be on the table at the start of the game. For example, most Whist variants that start with a standard pack of 52 cards are already playable.
You can play games where the rules change as the game goes along, or are made up by the players, or are too complicated to write as a computer program.
House rules are no problem, since the computer isn't enforcing the rules - you and your friends are.
Everyone can interact with different items on the game table, at any time. (Otter doesn't know about your game's turn-taking, so doesn't know whose turn it might be.)
We have played successful and fun online games of both Penultima and Mao with Otter.
The Otter game environment is accessed from a web browser running JavaScript, using a magic https link obtained from joining the game.
You will need to be able to talk to your friends about the game, while you play. Otter works well when used together with a voice chat - we have had success with Jitsi in voice-only mode.
Most relatively modern desktop browsers should be able to work with Otter. (The most advanced feature needed is support for WebAssembly.)
Otter currently has, in its pieces library:
Ingredients for chess, including fairy chess. So there's a board, pieces, including many fairy chess pieces, and a chess clock.
Ingredients for card games. So, a deck of 52 standard playing cards, plus two kinds of joker. Special "hand" and "deck" pieces for player hands and a pickup deck.
Currently there are game definitions for:
Penultima. This can be used directly to play standard chess and some fairy chess variants.
Mao. This can be used to play any game of roughly that shape.
Defining new games using the existing pieces from the library is fairly easy. It is also possible to add elements from the library ad-hoc, even while a game is in progress.
Currently, joining a game requires a unix shell account on the server host (or help from a shell account user).
There is not currently a publicly available server. The server code is Free Software and if you have a suitable vm or server you are encouraged to build and run it yourself, for you and your friends.
Mobile phones are not really suitable for playing on Otter because their screens are too small. Tablets and other touchscreen based systems could be made to work, but don't work well right now.
Otter does not currently have even a built-in text chat facility. It does have a way to share a URL for a voice chat.
Right now Otter is in a beta state. There are significant as-yet-unimplemented improvements that would make it work better for more people and more games. I don't currently promise savefile compatibility, or upgradeability, from one Otter version to the next. And there are still bugs.
Otter is Free Software. I wrote it to liberate game players from the
need to encode their game rules as computer programs and thus from the
tyranny of programmers :-).
I would love contributions, particularly to address the limitations I mention above, and to improve the user experience.
I am also working to make it possible to let users define their own games (including their own pieces, cards, boards, and so on) without having to install them on the server.
The Otter software project is hosted on Debian's GitLab, at https://salsa.debian.org/iwj/otter.
Merge requests (accompanied by a Signed-off-by indicating sign-off
of the Developer Certificate of Origin) would be very welcome.