This is a little guide on attack strength/damage calculation in Pokemon Vortex
With reasonable confidence the formula for Pokemon attacks is as follows:
Damage= Level times Base Power times STAB times Dark Bonus times Metallic Penalty times Other Modifiers divided by 60
where STAB=Same Type Attack Bonus, which is 1.5 if the Pokemon has the same type as the attack it is using, 1 if not
The Dark Bonus is 1.25 if your Pokemon is a Dark Pokemon, 1 otherwise
The Metallic Penalty is 0.75 if you are attacking a Metallic Pokemon, 1 otherwise
Other Modifiers includes Critical hits, which have a 1.5 modifier, and type effectiveness, which can be 0.25 (both the defending Pokemon's types resist your attack), 0.5, 1, 2, 4 (both the defending Pokemons types take double damage from your attack), or 0 (the defending Pokemon is immune to your attack)
The final calculation is then rounded off to give the damage dealt in game
Example: A L100 Charizard Mega X attacks a Metallic Pikachu with Blast Burn and hits
Therefore, Damage =100x150x1.5x1x0.75x1/60 (no critical hit, type effectiveness normal)
=281.25, which is rounded down to 281HP damage dealt
Notes:
Base power and types of moves can be found here
Pokemon types can be found here or in the Pokedex tab in Pokemon Vortex