Winter Bash 2014 Graphical Design

Merry Christmas, everyone; my expertise lies not in web design, though I have had a little experience in the past.

I really enjoy the design of the Winter Bash 2014 page. It is soothing to look at, not complicated to the eye and the colors blend really well.

I also noticed that the snow flakes would interact with your mouse over. This is totally rad.

So my question is, would one need jQuery to accomplish that or CSS would simply suffice to achieve the effect?

Would one at least need Photoshop to create graphics initially and then animate them? Or it is possible to accomplish all that just by using HTML, CSS, jQuery etc (I am just making a guess here)?

Happy holidays.