It's just a simple one-sprite homing missile. I'm not sure I can code to that missile can target multiple enemies. It uses the way (look at enemy's direction -> check with the original direction that missile was heading -> turn). You can use it anytime, but please give me credit.
hehe funny missile credits to pig005 for this idea go see the missile they made also press 1 2 3 and 4 for different amounts of missiles literally just touhou