We used to play find the sniper
we would have our ghillie guy stand by a tree
we would face the other way for a 30 count
then turn and try to spot him in the woods.
your instinct is to look for him behind things
His form breaking camo gear made him blend into the foreground,
so you started looking for a barrel or a mask glint
if he was tone tuned to the environment, he was really hard to spot, and we knew he was there.