Document probable font format

doc/formats/fonts.md

@@ -0,0 +1,35 @@
+# Fonts
+
+## *.fnt
+
+These are simple ASCII files. Here's an extract from `basfnt12.fnt`:
+
+```
+basfnt12.spr
+
+r  65  90   0  25  A-Z
+r  97 122  26  51  a-z
+r  48  57  52  61  0-9
+v  63      62      ?
+# ...
+
+done
+```
+
+The first line references a `.spr` file to read from. Then we have a list of
+records that must specify mappings of ASCII -> glyphs.
+
+First guess at the format:
+
+* `r | v` is `range` vs. `value`
+* Next we have the starting ASCII code
+* For `r`, we now have the finishing ASCII code
+* Next we have the starting position in the `.spr` file
+* For `r`, we now have the finishing position in the `.spr` file
+* Finally, just a comment?
+
+Assuming that's all true, `basfont12.fnt` has 86 entries. It looks like a normal
+[`.obj`](obj.md) file with... 86 entries. Good enough for me!
+
+There's also a `cboxfont` file, which seems to be junk. `cboxfont.spr` and
+`cboxfont.fmt` exist anyway. But who knows what else it might have in it.