It's my mission this year to become a wordpress developer. I've been using wordpress for years as a frontside user but I now want to be able to develop wordpress sites from themes to functionality and cms. I already have a great understanding of CSS & HTML and some PHP(It's been a while), is there a great course anyone can recommend? Or where should I start? What languages does one need to be strong in? HTMl, CSS, JAVASCRIPT & PHP?
Thanks in advance.