This post is a work in progress, please feel free to add or embellish...
Most of the details here come from balpha's
post.
Position
In order to simply show a position, just post the FEN string in a code block (put ``` on the line before and after). It will automatically be converted into a diagram.
Example:
```
r1br2k1/pp3ppp/2n2n2/1Bb3B1/8/2p2N2/PPP2PPP/R4RK1 w - - 1 13
```
This becomes:
r1br2k1/pp3ppp/2n2n2/1Bb3B1/8/2p2N2/PPP2PPP/R4RK1 w - - 1 13
Entire game
To display an entire game, paste the entire PGN in a code block after a FEN header. Most chess software allows you to copy/paste the PGN from a game. See Wikipedia if you want to type the PGN yourself.
The PGN you paste must include a FEN header. If you are starting from the start position, you can just include a blank FEN header:
```
[FEN ""]
1. f4 e5 2. g4 Qh4#
```
This becomes:
[FEN ""]
1. f4 e5 2. g4 Qh4#
Additional features
It is possible to enter entire variations and annotations for your games as well. If you simply copy/paste a pgn file from your external program, it will usually work correctly (after you add a FEN string). In order to enter variations, you can use parentheses for the variation moves. You can enter comments in curly braces too:
1. e4 e5 2. Nf3 Nc6 (2... Nf6 {Nf6 instead of Nc6 is called the Petroff Defense})
1. e4 e5 2. Nf3 Nc6 (2... Nf6 {Nf6 instead of Nc6 is called the Petroff Defense})
Variations can be nested as well.