Returns the top level selection, excluding prefabs.

This is the most common selection type when working with scene objects.

class LookAtMainCamera extends ScriptableObject {
    @MenuItem ("Example/Selection looks at Main Camera _l")
    
    static function Look() {
        var camera = Camera.main;
        if (camera) {
            for (var transform in Selection.transforms) {
                Undo.RegisterUndo(transform, transform.name + " Looks at Main Camera" );
                transform.LookAt(camera.transform);
            }
        }
    }
    //The menu item will be disabled if nothing, is selected.
    @MenuItem ("Example/Selection looks at Main Camera _l", true)
    static function ValidateSelection() {
        return Selection.transforms.Length != 0;
    }
}