One of the Deadpool movie’s best elements was how the movie brought his mask to life. This might shock you to learn, but there was an astounding amount of work involved in making a mask that could be as expressive as it is in the comics, but that Ryan Reynolds’ could still see and talk out of.

If you’ve ever wondered exactly why they didn’t just pull a fabric sock over Reynolds’ face, this featurette, via IGN, shows you. Plus, there’s the fun detail that the black eye sections were removable—so different ones with different white eye shapes could be put in. Serious amounts of engineering went into this mask.