Unfortunately both versions are separated, this means when purchasing the standalone you can't play the game in Steam, and when purchasing the Steam version, you can't play the standalone... it's a real pity that the Steam servers are having these massive problems today/yesterday. I hope that Valve fixes these issues as soon as possible.
If the issues still persist within the next hours, we will eventually shutdown our servers temporarily (in this case you can at least play the game in offline mode). I'm really sorry for these inconveniences, but unfortunately it's out of our control ![]()