Fix gyro ball base power (#206)

* Fix gyro ball base power

* Update gyro ball for gen6+

src/data/move.ts

@@ -1707,8 +1707,18 @@ export class BattleStatRatioPowerAttr extends VariablePowerAttr {
     const statThresholds = [ 0.25, 1 / 3, 0.5, 1, -1 ];
     let statThresholdPowers = [ 150, 120, 80, 60, 40 ];
 
-    if (this.invert)
-      statThresholdPowers = statThresholdPowers.reverse();
+    if (this.invert) {
+      // Gyro ball uses a specific formula
+      let userSpeed = user.getStat(this.stat);
+      if (userSpeed < 1) {
+        // Gen 6+ always have 1 base power
+        power.value = 1;
+        return true;
+      } 
+      let bp = Math.floor(Math.min(150, 25 * target.getStat(this.stat) / userSpeed + 1));
+      power.value = bp;
+      return true;
+    }
 
     let w = 0;
     while (w < statThresholds.length - 1 && statRatio > statThresholds[w]) {