wait just wondering matty why wouldn't this be O(n^2) (i dont have the code on front of me but...)
for each bullet in the bullet tlist
for each enemy in the enemy tlist
check if the bullet and enemy are within a certain distance of each other
if so, remove both
next
next
for each bullet in the bullet tlist
for each enemy in the enemy tlist
check if the bullet and enemy are within a certain distance of each other
if so, remove both
next
next