TomeNET

(4.14a) In-game metrics                                                         
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The lore is, that a grid in the game has a size of 10x10 ft, aka 3x3 metres.
Hence when a character has 40 ft infra-vision he will be able to spot monsters
detectable by infra-vision no further than 4 grids away from him.

However, since the game uses square grids instead of for example hexagonal
grids, this has some implications for moving:
Diagonal movement is more efficient than moving just horizontally and just
vertically when your target location is not exactly horizontally or vertically
away from you. Simply because by moving 1 grid diagonally you are twice as fast
as if you had moved to the same grid by first moving 1 grid vertically and then
1 grid horizontally.

While this seems sort of obvious, it is easy to miss that for example in the
'Dungeon Keeper' event whenever you enter another room, the next doors closest
to you are actually diagonal of you! So now it might become clear how to do
that event in the most effective way..

Note that the map coordinates you see when pressing SHIFT+L (CTRL+W with rogue
like keyset) can differ depending on if you have 'big_map' setting enabled or
not via  = b  .