lilvee1989 if you feel insecure, you can always put screenshot of your event or something. Vague question will always get vague response, however precise question will get either vague or precise answer, so go for the latter . The more specific you ask the better, that's why people will ask for capx, MINIMAL, not the full game.
This works similarly like a bug report though, narrow down the events you have problem with and upload the capx. Btw, problems with minimal capx attached always get good attention from the community.
On topic: probably like this? I'm just assuming what I think you wanted. You can use physic, but I think at your level, it is probably best to understand solid and bullet first. Deal with physic later when you have a good grasp of C2. Look around the behavior and instance variable I setup,try to make it elegant as your "homework".
Note: what you wanted from 1st post is z-ordering.