Will this attack do 0 damage?

Question

so far this is what I think

Shuckle
0 Atk IV
- 6 Atk
Bold Nature
- Constrict

vs

Shuckle@ Chilan Berry
EVs: 252 Def/ 252 HP
+ 6 Def
Bold Nature
Reflect
Aurora Veil
Friend Guard

Will this do 0?

Answer 1

No, Constrict would still deal 1 HP damage. This would remain the case no matter how many negative conditions you apply to the attacking Shuckle, or positive ones you give the defending one.

Though the damage calculator would absolutely round this attack down to 0, the game is programmed to make 0 damage impossible. It instead sets the damage to 1 HP when this happens.

The only time this doesn't occur is when you use a move like False Swipe on a Pokemon with 1 HP. In that case, the process is overridden and the damage stays at 0.

There is also a bug in Gen 1, and a different one in Gen 5, that allows you to deal 0 damage in particular circumstances. However, these are clearly development oversights.

More info

Comments

i can't see the Bug/Glitch in Generation 1, Bellsprout attacks Bulbasaur and takes 1 Damage and it's impossible to take 0 damage if a pokémon with false swipe and will attack with this move (if the opponent HP is red) takes 0 damage

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Each time Vine Whip ‘misses’, it is actually running the damage calculation and turning 0. The damage increases to 1 on the final turn because the Bellsprout used Growth. This is largely explained in the description of the video.