Action script 2.0 mobile game tutor

I'm building a game which is similar to space invaders. Their is a gun at the bottom of the screen moving left and right, which can shoot up at the aircraft. Their are free types of aircraft which should move independently. their should be no more then 3 aircraft on a screen at a time. I am currently finding it difficult to get my bullets to hit the aircraft's and need help. I also need the aircraft to shoot bullets down once in awhile and and this should increase as the game level progresses. The bullets from the gun should also be able to counter the bullets from aircraft. I will be sending you the work i have already done, and be asking you to help me in the creation of this mobile game. the code used must also be explained. thanks