See inside and select a background. Then, press the green flag and wait. It will take around 1 minute with a full black/blue image, and mabye even an hour with white/red.. I know, it's slow, but the effect is worth it, and i couldn't find a way to optimize it further.
Credits to @griffpatch for the color picker tutorial, and Toby Fox for his song Megalovania, which i remade in scratch as the notification that it finished
