Why are some shiny mons marked with square, while others are marked with star?

[stringDTD]

[theSLAYER]

1 hour ago, stringDTD said:

Because Gen 8 split shinies into two types of shiny, Square shiny and Star shiny.

[stringDTD]

@theSLAYER What does that mean? Could you please explain what's the difference and what/how the two different shinies are determined?

[theSLAYER]

14 minutes ago, stringDTD said:

@theSLAYER What does that mean? Could you please explain what's the difference and what/how the two different shinies are determined?

They just have different entrance animation. Functionally the same, for the most part.

Long story short, (PID High xor PID Low) xor (Full Trainer ID High xor Full Trainer ID Low) provides a remainder value ranging from 0 to 65535.

For Gen 6 and Gen 7, having this "xor'd value" (the answer/remainder) of 0 to 15 would lead to the mon being shiny.
[consequently, the xor'd result of 16 to 65535 would result in a non-shiny].

In Gen 8, they separated the xor result into categories:
0: Square Shiny
1-15: Star Shiny
16-65535: Non-shiny

However, there are a few exceptions where the mon will be a certain shiny no matter what:
Square Shiny: Shiny transferred from Pokemon GO (any xor'd value), Shiny that has Fateful Encounter flag (any xor'd value)
Star Shiny: Shinies caught in Max Lair can only be star (will only produce xor'd value of 1)

[Atrius97]

Here are examples of the entrance animations, Top is Square (XOR=0), Bottom is Star (XOR=1-15)

(Photos courtesy of Serebii.net: https://www.serebii.net/swordshield/shinypokemon.shtml)

Edited May 28, 2021 by Atrius97