Can anyone give me some advice on how to calculate an object trajectory? I want to use this for my alien game, where the enemy ship fires a missile directly you the player. This missile homes in on the player and heads towards him. The only solution I have come up with so far is to use the line algorithm. Store the screen co-ords in an array and turn by turn plot them. I suspect this method would need rotation for the missile to turn around..?? If anyone has any ideas then please forward them. No matter how crazy or simply. Remember it''s the simply ones that end up getting used. Thanks Indy