For my comment on https://nikles.it/2020/gamemaker-tutorial/better-moving-platforms/
Note that I have my own scripts for creating/destroying data structures, which help me track leaks. create_list() and unregister_and_destroy_list() won't work for you.
Additionally, I did not include the logic move_platform_y_downwards() and move_platform_y_upwards() because it's a light refactoring of what can be found in the tutorial.
move_platform_y():
/// @param yvel
var _yvel = argument0;
var _ydir = sign(_yvel);
//
// Create lists.
//
var colliding_instance_list = create_list("move_platform_y().colliding_instance_list");
var instances_that_have_moved_with_previous_xy_list = create_list("move_platform_y().instances_that_have_moved_with_previous_xy_list");
//
// Track if we hit a solid while moving.
//
var has_hit_solid = false;
//
// Move one pixel at a time.
//
repeat abs(_yvel) {
//
// Collided with solid.
//
if is_colliding_y(_ydir) {
has_hit_solid = true;
break;
}
if _ydir > 0 {
if !move_platform_y_downwards(
colliding_instance_list ,
instances_that_have_moved_with_previous_xy_list ) {
has_hit_solid = true;
break;
}
} else if _ydir < 0 {
if !move_platform_y_upwards(
colliding_instance_list ,
instances_that_have_moved_with_previous_xy_list ) {
has_hit_solid = true;
break;
}
}
//
// Move the platform.
//
y += _ydir;
}
//
// Destroy data structures.
//
unregister_and_destroy_list(colliding_instance_list);
unregister_and_destroy_list(instances_that_have_moved_with_previous_xy_list);
//
// Return.
//
return !has_hit_solid;