No online play sadly, but it's the best game I've bough this year.
All the negative comments like repetitive etc... could be directed just as easily towards Diablo, Diablo II and no doubt Diablo III.
Shadowgrounds Survivor is just great fun to play, even solo. The levels look great (not just great GFX, but they really help with atmosphere) and playing the game at lower resolutions actually gives the game a groovy, retro feel.
For $20 (on Steam) you can't go wrong with this game. Diablo III might be getting the column inches, but apart from the lack of online play, this game deserves to be bought.