why did i win this?

http://www.chess.com/livechess/game?id=1035002737

i misplayed the opening and blundert a pown and than i won the endgame while beining down a pown. why did i win this? and how could my opponent have prevented this?

if you look your pawns can only take other pieces diagonaly and they blocked every square around his king, while your bishop blocked him from moving forward or downwards, but there is nothing that puts the king in check to force him to move so i dont know why you won, but if he wanted to get out the only thing i can think of is taking out the undefended pawns as he does not have all of them protected

His 34. d4+ is a deadly mistake. It's a force win for black. Though prior to that move, white is only playing for a draw.