Item Missile?

[dj Jo]

I'm trying to remake the map, Path Defence from starcraft
but I need to know how to do this...

(like in Battleships and Battletanks...) Acquire an item that makes you automatically shoot projectiles at enemies when they come near you

I just need to know how to do that then I would be fine making the rest of the map

PS I'm new around here lol, hi there!