Same Nationality Breeding without Ditto:

Already implemented.

Same Nationality Breeding with Ditto:

DW calc is not present. Everything else after that is shifted to accommodate this loss.

International Breeding without Ditto:

Calculate the PID once (n), then again (n+2), then again (n+4), and again (n+6). If one is shiny, stop. Else stop at n+6.

International Breeding with Ditto:

Still being tested. If same, Calculate the PID once (n), then again (n+2), then again (n+4), and again (n+6). If one is shiny, stop. Else stop at n+6.

I suspect that everstones will NOT change any calculation routine, meaning that Everstones will work for the Masuda Method. Also we have to make sure there's no difference for the male + ditto, but this is highly unlikely. I'll update this later with the routine.

Ditto + IV Inheritance:

Ditto will always give the A no matter the positioning (while female is B)

Ditto will always give the B no matter the positioning (while a male is A)

International with Everstone yielded different results, have to test more later.

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@bonds post

0000-FFFF x2 = 16^8 possibilities

0-F x2 = 16^2 possibilities

24-32 = 9 possibilities

16^10 * 9 = 9 trillion possibilities :S