Valve's Doug Lombardi let slip the good news in an interview with Fast Company, but left the details vague.
"We will be announcing some DLC for it, so folks can keep a look out for more content coming this summer. We'll be putting more details out about that in a week or so.
"We'll support that with more videos or more comics," Lombardi said.
I personally don't like puzzle games all that much, a bit too slow for my tastes