Generation II changed 34 things: 4 type chart cells, 2 types added, 22 move stats, 4 move types and 2 species types

Every row dated to Generation II, grouped by kind. Before is the value through Generation I, after is the value from Generation II.

Main-series rules that PokéAPI records as past values, plus the ordinary type chart by era; default forms only.

Type chart cells

4 matchups changed value

Type	Field	Before	After
Bug	against Poison	×2	×½
Ghost	against Psychic	×0	×2
Ice	against Fire	×1	×½
Poison	against Bug	×2	×1

Types added

Type	Field	Before	After
Dark	new type	None	Dark
Steel	new type	None	Steel

Move stats

Move	Field	Before	After
Bite	effect chance	10%	30%
Blizzard	accuracy	90%	70%
Dig	power	100	60
Dizzy Punch	effect	Inflicts regular damage with no additional effect.	Has a chance to confuse the target.
Dizzy Punch	effect chance	0%	20%
Double-Edge	effect	User receives 1/4 the damage it inflicts in recoil.	User receives 1/3 the damage inflicted in recoil.
Double-Edge	power	100	120
Explosion	power	170	250
Fire Blast	effect chance	30%	10%
Gust	effect	Inflicts regular damage with no additional effect.	Inflicts regular damage and can hit Pokémon in the air.
Poison Sting	effect chance	20%	30%
Psychic	effect chance	30%	10%
Rock Slide	effect	Inflicts regular damage with no additional effect.	Has a chance to make the target flinch.
Rock Slide	effect chance	0%	30%
Rock Throw	accuracy	65%	90%
Self-Destruct	power	130	200
Sky Attack	effect chance	10%	30%
Thunder	effect chance	10%	30%
Tri Attack	effect	Inflicts regular damage with no additional effect.	Has a chance to burn, freeze, or paralyze the target.
Tri Attack	effect chance	0%	20%
Whirlwind	accuracy	85%	100%
Wing Attack	power	35	60

Move types

Move	Field	Before	After
Bite	type	Normal	Dark
Gust	type	Normal	Flying
Karate Chop	type	Normal	Fighting
Sand Attack	type	Normal	Ground

Species types

Species	Field	Before	After
Magnemite	types	Electric	Electric and Steel
Magneton	types	Electric	Electric and Steel