LiraNuna who was quite active two years ago, has released a small technical demo called “Blending Demo”.
This demo was written to demonstrate how easy it is to utilize the DS’s hardware blending and create impressive effects with no effort. In this demo, the witch is flying in the sky, and whenever she’s hovering between the moon, she turns black, because the light from the moon illusions it as such.
The demo is composed of 2 backgrounds and a sprite. The sprite is set to blend with the first background (the moon) with 0 blending, resulting the black color.
Thanks to Sir Brakken VI of http://www.tehskeen.com for this excellent news hint.