Unity

If you want a really solid, structured course, Udemy has a lot of really good video coursewares that are all at-your-own-pace. This one looks pretty great and starts you from the very basics if you don't have experience with programming previously.

(If the price seems a bit high, sign up for Udemy, ♥ the course, and within a few hours it magically goes on sale for like 80% off. They're aggressive and automatic with their discounting)