Docs: instance_select

The instance select functions can be used without the Tweenline Engine, but they are useful when you combine them with tween_stagger_* functions.

They are used to create an array of instances

For example:

// First create an array with obj_box_small1 and obj_box_small3 objects's ids.
var inst = [obj_box_small1, obj_box_small3];

// Then, pass the array, and filter each instance by the x position
// It has to be less than ("<")
// the value of the x position of the yellow box (obj_box_small2.x)
// Then, sort the result by the y position value of each box in ascending
var arr = instance_select_filter_sort(inst, "x", "<", obj_box_small2.x, "y");

// Finally, you can stagger all instances: (grouped by waves of 10 instances)
tween_arr = tween_stagger_to(arr, 2, ["angle",360, "blend",c_red], .5, 10);