Hi everyone, there appears to be a problem logging in right now. It seems that the Steam Web API is down - we use that to login / authenticate and tie your steam account to your game account.
If you ever have login / connectivity problems you can check https://steamstat.us/ to check the status of the Steam Web API. Of course feel free to report any problems to us, but in this case the best we can advise is to wait for Valve to fix.