diff --git a/BigBoxOfHTML.md b/BigBoxOfHTML.md
index 1c5c5b2..cc881cd 100644
--- a/BigBoxOfHTML.md
+++ b/BigBoxOfHTML.md
@@ -30,6 +30,7 @@
  - [Stickers.js](http://stickerjs.cmiscm.com/) - Apply an (interactive!) sticker effect to an image
  - [Stretchy](http://leaverou.github.io/stretchy/) - Easy form element autoresizing
  - [wallop](http://pedroduarte.me/wallop/) - Library to show / hide stuff, includes a previous / next system.
+ - [houdini](https://github.com/cferdinandi/houdini/) - A super simple script to make an element collapsible.
 
 ## Accessibility
  - [abbr-touch](https://github.com/Tyriar/abbr-touch) - Make the `title` attribute of the `<abbr>` (abbreviation) HTML element accessible to touch screen users