Hidden Bookshelf - L4D2 Custom Map (Authoring Tools, SourceSDK, Hammer, etc...)

took a long ass time making this bookshelf move to reveal a hidden room in my L4D2 custom map. It's essentially a func_linear with a bookshelf prop_dynamic_override and a func_button parented to it. You press button, f_linear moves, the prop and invisible button follow. Very easy but took ages to do.