before change to polygon

core/src/com/trs/game/model/Model.java

@@ -20,10 +20,10 @@ public class Model {
     }
 
     public void timerStep(){
-        monster.move();
+        monster.move(walls);
 
         for(Projectile projectile : projectiles){
-            projectile.move();
+            projectile.move(walls);
         }
     }
 

core/src/com/trs/game/model/Monster.java

@@ -4,6 +4,8 @@ import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 import com.trs.game.StaticMath;
 
+import java.util.ArrayList;
+
 public class Monster {
 
     private final int SPEED = 3;
@@ -42,7 +44,7 @@ public class Monster {
         renderer.end();
     }
 
-    public void move(){
+    public void move(ArrayList<Wall> walls){
         checkTarget();
 
         this.xPos += this.movementX;

core/src/com/trs/game/model/Projectile.java

@@ -1,8 +1,14 @@
 package com.trs.game.model;
 
 import com.badlogic.gdx.math.Circle;
+import com.badlogic.gdx.math.Intersector;
+import com.badlogic.gdx.math.Polygon;
+import com.badlogic.gdx.math.Rectangle;
 import com.trs.game.StaticMath;
 
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+
 public class Projectile {
 
     private final int SPEED = 3;
@@ -22,15 +28,40 @@ public class Projectile {
         movementY = Math.sin(angle) * SPEED;
     }
 
-    public void collision(){
 
-    }
 
-    public void move(){
+    public void move(ArrayList<Wall> walls){
+        checkCollision(walls);
+
         circle.x += this.movementX;
         circle.y += this.movementY;
     }
 
+    private void checkCollision(ArrayList<Wall> walls){
+        for(Wall wall : walls){
+            if(Intersector.overlaps(circle, wall.getRect())){
+
+                circle.x -= movementX;
+                circle.y -= movementY;
+
+                collision(wall);
+                break;
+            }
+        }
+    }
+
+    private void collision(Wall wall){
+        System.out.println("Collision");
+
+        double alpha = Math.atan(movementY/movementX);
+        double delta = (Math.PI / 2) - Math.toRadians(wall.getRotation());
+        double beta = +((Math.PI / 2) - alpha - delta);
+        double phi = beta + Math.toRadians(wall.getRotation());
+
+        movementX = Math.cos(phi) * SPEED;
+        movementY = Math.sin(phi) * SPEED;
+    }
+
     public int getxPos() {
         return (int) circle.x;
     }