You can do that or just put random (min,max) and just use the right degrees...I do it in my app. Since obviously a circle is 360 degrees...doing it this way would not make it sharply diagonal left or right, but also everything in between. Just depends what you are going for.
if you do it like that, it can go in any direction between the min and max so it can go striaght for example, i think he only wants diagonal left or right. but that works too
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make a rule in the actor you spawn when randommove=0
then put in a move behavior and set the direction diagonally left and have it relative to scene
make another rule and have when attribute randommove=1
then put a move behavior in there set the direciton diagonally right and relative to scene
then when you spawn that actor have a change attribute behavior wherever changing attriubte randommove to random(0,1)