It's SYSTEM; compare values, if player.X > enemy.X - enemy - set mirrored
Where would the "for each" go there and how?
If you only use a System, then you are not doing any picking of specific enemies, then a For each wont help you.
Here is some example of how it works. You have a player (Green square) and 3 enemies (Red squares) and an approx. distance of 400 between the player and the last enemy. Each Enemy also have a Variable called "Enemy_Alive" and going to use distance and that variable to change the color of valid enemies.
So in the first example, not using a For each. I haven't specified which enemies to check the distance against, And even though 2 of them are within range they do not change color.
Example two is the same as the first, except it uses for each, so it will check distance for each of the enemies. And 2 of them change color.
In the last one, they are all within distance, but a condition where they also have to be alive is needed, and only the middle one is alive so it changes color.