Two things, the first, probably already known. Flutter Mane's tera type was not automatically changed to electric in the calculator (see image below).
Second thing: It would be very useful for the calculator to update items according to the damage received (the same would apply if the opposing Pokémon takes less damage because it is holding the item Eviolite, Assault Vest, etc).
For example. Look at this turn:
Turn 13
Wugtrio, come back!
Go! Tatsugiri (
Tatsugiri-Droopy)!
The opposing Gallade used
Leaf Blade!
(Tatsugiri lost 59% of its health!)
We know that Gallade's possible items are:
Items: Life Orb (55%), Choice Band (23%), Choice Scarf (22%)
He is not choice banded because if it were, it would take more hp from Tatsugiri-Droopy:
Lvl 84 84 Atk Choice Band Sharpness Gallade Leaf Blade vs. Lvl 82 84 HP / 84 Def Tatsugiri: 214-252 (86.9 - 102.4%) -- 18.8% chance to OHKO
It is also not Life Orb, for two reasons: If it were, it would also take more hp from Tatsugiri-Droopy:
Lvl 84 84 Atk Life Orb Sharpness Gallade Leaf Blade vs. Lvl 82 84 HP / 84 Def Tatsugiri: 185-218 (75.2 - 88.6%) -- guaranteed 2HKO
And also for not losing HP from Life Orb (in Gen 8 for example, Magic Guard users normally wouldn't lose HP from Life Orb)
So it's 100% Choice Scarf by elimination and also because of the damage taken:
Lvl 84 84 Atk Sharpness Gallade Leaf Blade vs. Lvl 82 84 HP / 84 Def Tatsugiri: 142-168 (57.7 - 68.2%) -- guaranteed 2HKO
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Then the calculator would automatically change the item to a Choice Scarf. This would save time in terms of manually checking each time. Yes, some situations are more complex than others, which is why I suggest the following. Let's take any example.
A pokémon X has 3 possible items. Choice Specs (50%), Leftovers (30%) and Heavy-Duty Boots (20%). By default, the calculator always shows the most recurring item, in this case Choice Specs. But, upon receiving damage, it is noted that it is not Choice Specs. In this case, the Calculator would switch to the second most recurring item: Leftovers.