Here are the first few moves:
1.c4 e5 2.Nc3 Bb4 3.Nd5 Bc5 4.Nf3 e4 5.d4 Bf8
After the fifth move, black has essentially only pushed one pawn, while while has developed two knights and his c-pawn and d-pawn. However, the current position does not seem bad for black at all. 365chess.com gives winnings percentage White / Draw / Black as 25% /50% /25%.
[fen ""] 1.c4 e5 2.Nc3 Bb4 3.Nd5 Bc5 4.Nf3 e4 5.d4 Bf8
My question is, in the first few moves, has black violated any opening principles? Why this position is not too bad for black while he has only pushed one pawn while white has developed two nights (and it is white's turn now)?