Collision

This will (probably) help, but I need patience to look through it and then transfer it to my scenario. Now I think the question from the beginning of this discussion is answered :) .

The blue box is just a sample box. You can press the 'h' key to hide the box and have it set what random object it will spawn. When hidden, you can pass through it except when hitting it from underneath, when it will become visible and spawn a random object to collect (I just created a Coin object and changed the image to show what random value was selected). It would be just as easy to have a specific value held by the box and spawn a specific type object when hit. In the sample, you can repeatedly spawn an object and pick it up each time you hide the box; but, of course, in a normal scenario, you would have it only work one time.