I had a pirated copy of WC3 available to me via a vulnerability in my school's AD setup which allowed me to access another student's directory where it was installed.

I would play it almost exclusively in a web design class I took. That class was where I learned HTML; that wasn't the focus of the class, not by a long shot, but it was the thing that captured my interest the most. I ignored everything else in that class in favor of the Wintermaul Tower Defense custom map.