Grimer Eyes
5.4.00
Recent investigation into the Z80 code that runs
the Pokemon GameBoy game has revealed a lot of useful information.
Most notably is the main formula that runs the combat engine of Pokemon
Red/Blue/Yellow and Pokemon Stadium. As in all games, Damage from an
attack is a calculation based on stats, and frequently including a random
variability. Pokemon is no different. Extracted from the Z80
code, this is the formula to determine how much damage your Pokemon does:
[[[[[[2*A/5 +2] *B*C/D] /50] +2] *X*Y/10] *Z/255]
A = Attacker’s Level
B = Attacker’s Attack or Special (Depending on type of attack)
C = Strength of Attack
D = Defender’s Defense or Special (Depending on
type of attack)
X = 1.5 if type of attack matches attacker’s type,
otherwise X = 1
Y = 20 if defender is weak to attack
5 if defender is resistant to attack
0 if attack has no effect on defender
(i.e. normal attack on ghost)
10 in all other cases
Z = Random number from 217 to 255
Important note about the formula, sections enclosed
in []’s must have normal mathmatetical rules run within them, but the
final value must be rounded down to the closest integer.
So: [2 * 2 / 5 + 2] becomes [2.8] which then
becomes 2 before you can proceed with the rest of the formula.
A full example:
My Level 2 Rattata with an attack of 12, uses
Tackle (Strength 35) against a Pidgey (Defense of 15). The Random
number for Z was 223...
[[[[[[2 * 2 / 5 + 2] * 12 * 35 / 15] / 50] + 2] * 1 *
10 / 10] * 223 / 255]
[[[[[[2.8] * 12 * 35 / 15] / 50] + 2] * 1 * 10 / 10]
* 223 / 255]
[[[[[2 * 12 * 35 / 15] / 50] + 2] * 1 * 10 / 10] *
223 / 255]
[[[[[56] / 50] + 2] * 1 * 10 / 10] * 223 / 255]
[[[[1.12] + 2] * 1 * 10 / 10] * 223 / 255]
[[[1 + 2] * 1 * 10 / 10] * 223 / 255]
[[3 * 1 * 10 / 10] * 223 / 255]
[[3] * 223 / 255]
[3 * 223 / 255]
[2.6235294118]
2
- Bret Larwick