The usual convention is to name openings by White 'Attack' or simply 'Opening'. Openings by Black we might call 'Defence' or, possibly, Counter-Attack. Time was, a gambit essayed by Black would be called a 'Counter-Gambit', but that expression seems archaic these days. So here: King's Pawn Opening.

I thought that a counter-gambit was when instead of accepting the pawn's sac (the gambit), the opponent proposes another pawn's sac. As in 1. d4, e5, 2. d4, e5.

Very occasionally an opening might be called 'Game'. With this reply, we have a Mutual King's Pawn Game'. It is probably too much to say that the Sicilian Defence 1...c5 is actually better - premature at least - but the latter is the more popular these days. @damalfi - consider the Greco Counter-gambit: 1.e4 e5 2.Nf3 f5. You might recognise it as the Latvian Gambit in modern parlance, but I prefer the older appellation. You will see that Black's gambit is not in response to one by White.

The Giuoco Piano Opening - the Quiet Game. It can increase very sharply in volume, however!

This move is fine, if a little non-committal.

Giuoco Pianissimo. Careful, solid, but not what you'd call aggressive.

Now the position is altogether symmetrical. Probably the game is still accordingly level, but Black should beware of carrying the symmetry too far, lest he finds White's extra tempo prove decisive.

That's incredible. An 8. move's symmetry... will give the win to white.

There doesn't seem to be much against it. White could immediately try 9.Nxf6 but Black can safely maintain the symmetry. He could as well try 9.Bxf6, whereat it would be dangerous for Black to maintain the symmetry: 9...Bxf3? 10.Bxd8 Bxd8 11.Be7 Be7 12.c3 c3 13.cxd4 cxd5 14.exd5 exd4 15.Re1 wins the exchange. A whole alternative idea is 9.b4 possibly in association with c3.

It is very interesting to try to find out where the symmetry will favour white. Thank you ion, your comments are always really interesting.