add sport effects back

include/constants/battle_config.h

@@ -119,6 +119,7 @@
 #define B_HIDDEN_POWER_DMG          GEN_7 // In Gen6+, Hidden Power's base power was set to always be 60. Before, it was determined by the mon's IVs.
 #define B_ROUGH_SKIN_DMG            GEN_7 // In Gen4+, Rough Skin contact damage is 1/8th of max HP instead of 1/16th. This will also affect Iron Barbs.
 #define B_KNOCK_OFF_DMG             GEN_8 // In Gen6+, Knock Off deals 50% more damage when knocking off an item
+#define B_SPORT_DMG_REDUCTION       GEN_7 // In Gen5+, Water/Mud Sport reduce Fire/Electric Damage by 67% instead of 50%
 
 // Type settings
 #define B_GHOSTS_ESCAPE             GEN_7 // In Gen6+, abilities like Shadow Tag or moves like Mean Look fail on Ghost-type Pokémon. They can also escape any Wild Battle.

src/battle_util.c

@@ -8321,6 +8321,9 @@ static u32 CalcMoveBasePowerAfterModifiers(u16 move, u8 battlerAtk, u8 battlerDe
         MulModifier(&modifier, (B_TERRAIN_TYPE_BOOST >= GEN_8) ? UQ_4_12(1.3) : UQ_4_12(1.5));
     if (gFieldStatuses & STATUS_FIELD_PSYCHIC_TERRAIN && moveType == TYPE_PSYCHIC && IsBattlerGrounded(battlerAtk) && !(gStatuses3[battlerAtk] & STATUS3_SEMI_INVULNERABLE))
         MulModifier(&modifier, (B_TERRAIN_TYPE_BOOST >= GEN_8) ? UQ_4_12(1.3) : UQ_4_12(1.5));
+    if ((gFieldStatuses & STATUS_FIELD_MUDSPORT && moveType == TYPE_ELECTRIC)
+     || (gFieldStatuses & STATUS_FIELD_WATERSPORT && moveType == TYPE_FIRE))
+        MulModifier(&modifier, (B_SPORT_DMG_REDUCTION >= GEN_5) ? UQ_4_12(0.67) : UQ_4_12(0.5));
 
     return ApplyModifier(modifier, basePower);
 }