Loading this into the strongest available engine ( Houdini 1.5a ) gives the assessment of +0.2 in black's favour after 12...Bc7 13.c3
Mmm, let's look. 12...Bc7 13.c4 ! instead of 13.c3
a/ 13...Nb4 14.Nf6+ !!! What a sacrifice - white wins on brute force.
a1/ 14...Kh8 15.Qe4 g6 16.Qh4 winning
a2/ 14...gxf6 15.Bxh7+ Kxh7 ( after Kg7 and Kh8 follows a "quick" mate in 6 ) 16.Qh5+ Kg8 ( Kg7 is mate in 5 ) 17.gxf6 Qxd4+ ( all other moves mate quickly ) 18.Rf2 and black is helpless against the threats Rg2 and Qg5
b/ 13...Ne7 14.Be3 defending d4 first. My book "Attack with the Blackmar Diemer" stopped here, saying black is slightly better.
The problem now is that after 14...Nd7, black has no weakness and can start to counterattack and possibbly exchange with moves like Nf5, or increasing the pressure on d4 with Bb6.
So it is clear that 13.c4 is spectacular, but rather wishfull thinking chess, hoping for 13...Nb4
Deviating on move 13 is no option either, as 12...Bc7 13.Qh5 is also insufficient, as 13...Nd7 gives black a small edge.
Hodini shows no improvement on move 12, so probably 11.00 was premature - but more on this next blog.
fyi - Scheerer only considers 10...Bd6 11.00 Qe7 ?! , but does not even mention blac's strongest reply 11...00.