I used Greenfoot's getOneIntersectingObject(Obstacles.class) function. It uses the image of both the player and obstacles objects to detect collisions with the object "Obstacles". For example in the player movement code after the player moves right a while block runs to move the player outside the bounds of the image of "Obstacles" object. pseudo code: if ("right" key is down) { move Player right by X } while (getOneIntersectingObject(Obstacles.class) != null) { Move Player to the left one }

Try while(getOneObjectAtOffset(getImage().getWidth()/2+1, 0, Obstacles.class)!=null) { setLocation(getX()-1, getY()); }

Amazing work! Some advices I may give is you die at the end of a level and you can't get to the next level. Also, you could make the background and music change in every level. You can also create other enemies or objects. All the others are perfect!