Just want to help people save some money:
The filing fee is $35 however that is for an entire file of associated work.
So you can put all your created artwork, sprites, music, sound effects, screen shots, layout and events sheets and anything associated with a game and file it all for that $35 as a compilation work.
Just be sure it is all your own work and that is how I file my copyrights for media all the time.
I would be happy to explain DMCA take down notices to get your copyrighted work taken down and the legal process of copyright litigation if anyone is interested?
I have done DMCA takedowns several times over the years.