@strangemover unfamiliar territory is a good phrase. Very apt. If only I could believe that he decided to play a5 because he didn't know what else to do... *eyeroll*
Well of course unlikely. But who knows his motivations and thoughts? Perhaps he was tilting, perhaps just decided on a whim to push the flank pawns, whatever. The point remains that you just have to beat what's put in front of you, this is the great thing about chess - every game is different. Sure you are entitled to block whoever you like for whatever reason, just as your opponents are entitled to play whatever moves they like for whatever reason.
Mock me all you want. It's not like I can do anything to stop it, so *shrugs*.