Add new mountain background

src/battle-phases.ts

@@ -242,7 +242,7 @@ export class EncounterPhase extends BattlePhase {
 
   doEncounter() {
     if (startingWave > 10) {
-      for (let m = 0; m < Math.floor(startingWave / 10); m++)
+      for (let m = 0; m < Math.min(Math.floor(startingWave / 10), 99); m++)
         this.scene.addModifier(getPlayerModifierTypeOptionsForWave((m + 1) * 10, 1, this.scene.getParty())[0].type.newModifier());
     }