easier to take nuclear land if most of the land are nuclear (#241)

- **Revert "Change BorderTiles from Array to Set (#230)"**
- **easier to take nuclear land if most of the land are nuclear**

src/core/configuration/Config.ts

@@ -163,7 +163,7 @@ export interface Config {
   tradeShipSpawnRate(): number;
   defensePostRange(): number;
   defensePostDefenseBonus(): number;
-  falloutDefenseModifier(): number;
+  falloutDefenseModifier(percentOfFallout: number): number;
   difficultyModifier(difficulty: Difficulty): number;
   // 0-1
   traitorDefenseDebuff(): number;

src/core/configuration/DefaultConfig.ts

@@ -126,8 +126,10 @@ export class DefaultConfig implements Config {
     return 250_000;
   }
 
-  falloutDefenseModifier(): number {
-    return 5;
+  falloutDefenseModifier(falloutRatio: number): number {
+    // falloutRatio is between 0 and 1
+    // So defense modifier is between [5, 2.5]
+    return 5 - falloutRatio * 2;
   }
 
   defensePostRange(): number {
@@ -374,8 +376,9 @@ export class DefaultConfig implements Config {
     }
 
     if (gm.hasFallout(tileToConquer)) {
-      mag *= this.falloutDefenseModifier();
-      speed *= this.falloutDefenseModifier();
+      const falloutRatio = gm.numTilesWithFallout() / gm.numLandTiles();
+      mag *= this.falloutDefenseModifier(falloutRatio);
+      speed *= this.falloutDefenseModifier(falloutRatio);
     }
 
     if (attacker.isPlayer() && defender.isPlayer()) {