Sierpinski carpet animation:
Cwgreene, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Animated_Sierpinski%27s_carpet.gif
Menger sponge animation:
Wattcle, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Menger_sponge_rotation.gif
