It's more than odd to be posting about DLC for a game that came out almost exactly two years ago, but then I think it's more than odd that dogs don't just crap all over their owners' bedroom floors, so you shouldn't take my surprise seriously.
Revenge of the Titans
was/is an excellent and ferocious tower defence/RTS game from the redoubtable UK indie Caspian 'Puppy Games' Prince, and Jim
both fell for its unforgiving pixel-art charms back in 2010. And now it has DLC of a sort, in the form of a sandbox mode with which to battle the deathless space invader hordes on your custom-chosen terms.