Why? You could reprogram everything so that you could use sprites instead. With that, you can do also fancy postprocessing. Another reason for not using panels is that their coordinates, even though they are typed as var's, are snapped for drawing to integer coordinates. So, doing things like ->pos_x += 5 * time_step results in jittered motion.

For RUDI, I have done falling snowflakes in the main menu with panels - the only solution to this was clamping fps_max and doing something like pos_y -= 1 each frame --- without the use of time_step. So, I rely upon the fact, that a regular computer renders the main menu with, say, 60 fps.

For the credits, I have falling snow flakes, too, but this time I did everything in world space with sprites and so on. Here, I safely do ->z -= 5 * time_step or so. Another advantage is that rotated panels are not properly filteres as their sprite-counterparts in world space.

Another advantage is that you have problems with the monitor resolution - if you do everything with sprites you can simply switch the resolution and the sprites don't change their relative size on the screen as if it happens when you use panels.

Don't use panels for 2D games!