app/src/main/java/school_project/Vec2.java

@@ -31,6 +31,10 @@ public class Vec2 implements Serializable {
         return new Vec2(x + o.x, y + o.y);
     }
 
+    public Vec2 sub(Vec2 o){
+        return new Vec2(x - o.x, y - o.y);
+    }
+
     @Override
     public String toString() {
         return "("+x+","+y+")";