How to make custom maps?

[Chazar]

@Gandalf: That's not what I meant. I was referring to the problem of selecting a province within the game, which select the closest white pixel to the clicking point, but not necessarily the intended one on maps with province boundaries drawn...

[Kristoffer O]

@ bone_daddy: reddish borders are useful if you don't want to specify every neighbour of every province. The computer uses red colours to guess neighbours. You will probably have to check on all provinces to make sure that they work properly, but it will save you some clicking trouble. Bright red and symmetrical borders will give you a good map file. More brownish or very thin borders, strangely shaped provinces or sea areas will leave you with some provinces with too many neighbours.