Allow enemies move by difficult mode

src/com/annimon/influencexxii/EnemiesController.java

@@ -15,6 +15,7 @@ public class EnemiesController {
     
     public EnemiesController() {
         enemies = new Array<Enemy>();
+        difficultMode = 0;
     }
     
     public void setScreenParameters(float width, float height) {
@@ -35,10 +36,12 @@ public class EnemiesController {
     }
     
     public boolean isCollide(float x, float y) {
+        boolean collide = false;
         for (Enemy enemy : enemies) {
-            if (enemy.isCollide(x, y)) return true;
+            enemy.update(x, y, screenWidth, screenHeight, difficultMode);
+            if (enemy.isCollide(x, y)) collide = true;
         }
-        return false;
+        return collide;
     }
     
     public void killEnemy(float x, float y) {

src/com/annimon/influencexxii/Enemy.java

@@ -2,6 +2,7 @@ package com.annimon.influencexxii;
 
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
+import com.badlogic.gdx.math.MathUtils;
 import com.badlogic.gdx.math.Rectangle;
 import com.badlogic.gdx.math.Vector2;
 
@@ -33,4 +34,51 @@ public class Enemy {
         renderer.setColor(color);
         renderer.rect(rect.x, rect.y, rect.width, rect.height);
     }
+    
+    public void update(float px, float py, float scrWidth, float scrHeight, int difficultMode) {
+        if (difficultMode == 0) return;
+        
+        final int speed = 1 + difficultMode / 3;
+        changeCoords(speed);
+        boolean changeDir = validateToScreen(scrWidth, scrHeight);
+        
+        switch (difficultMode % 3) {
+            case 2: // Medium
+                if (rect.contains(px, py)) {
+                    rect.x += dir.x * speed;
+                }
+                break;
+            case 0: // Difficult
+                if ( (rect.contains(px - 3, py - 3)) || (rect.contains(px + 3, py + 3)) ) {
+                    if (Math.abs(dir.x) < 0.2f) dir.x = MathUtils.random(-1f, 1f);
+                    if (Math.abs(dir.y) < 0.2f) dir.y = MathUtils.random(-1f, 1f);
+                    changeCoords(speed);
+                }
+                break;
+        }
+        
+        if (changeDir) inverseDirection();
+        else if (MathUtils.random(50) == 10) {
+            changeDirection();
+        }
+    }
+    
+    private void changeCoords(int speed) {
+        rect.x += dir.x * speed;
+        rect.y += dir.y * speed;
+    }
+    
+    private void changeDirection() {
+        dir.x = MathUtils.random(-1f, 1f);
+        dir.y = MathUtils.random(-1f, 1f);
+    }
+    
+    private void inverseDirection() {
+        dir.scl(-1f, -1f);
+    }
+    
+    private boolean validateToScreen(float width, float height) {
+        Rectangle screen = new Rectangle(0, 0, width, height);
+        return (!screen.contains(rect));
+    }
 }