  According to the standard protocol of spatial public goods game, a cooperator
player invests not only into his own game but also into the games organized by
neighboring partners. In this work, we relax this assumption by allowing
cooperators to decide which neighboring group to prefer instead of supporting
them uniformly. In particular, we assume that they select their most successful
neighbor and focus external investments exclusively into the related group. We
show that this very simple alteration of the dynamical rule results in a
surprisingly positive evolutionary outcome -- cooperators prevail even in harsh
environment represented by small values of the synergy factor in the game. The
microscopic mechanism behind the reported success of the cooperator strategy
can be explained by a blocking mechanism which affects the propagations of
competing strategies in a biased way. Our results, which remain intact by using
different interaction topologies, reveal that it could be beneficial to
concentrate individual efforts to reach a higher global wellbeing.
