The Intersection_For_Loop is geared specifically for constructing intersections of polyhedra created inside a loop. `

$fn=30;
intersection_for(i=[0:1]){

    translate([0, 0, 0.8 * i])
    sphere(r = 1);
    
}

`

Confusingly, wrapping a for loop in an intersection creates a union.

$fn=30;
intersection(){
    for(i=[0:1]){
        translate([0, 0, 0.8 * i])
        sphere(r = 1);
    }
}