It's a Grünfeld, surprisingly. Here are the moves so far, up to now all blitzed out:
Topalov-Anand, Game 1:
1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.cxd5 Nxd5 5.e4 Nxc3 6.bxc3 Bg7 7.Bc4 c5 8.Ne2 Nc6 9.Be3 0-0 10.0-0 Na5 11.Bd3 b6 12.Qd2 e5 13.Bh6 cxd4 14.Bxg7 Kxg7 15.cxd4 exd4 16.Rac1 Qd6 17.f4 f6 18.f5 Qe5
Only now is Topalov starting to think, and now he has played 19.Nf4. Some brief comments:
While the 10...Na5, 11...b6, 12...e5 line is far from unknown, it isn't the main drag, either. But it happened in a very big game: game 1 of the Topalov-Kamsky Candidates Match last year. There Topalov played 16.f4 immediately, and after 16...f6 the very direct 17.e5. The game ended in an exciting draw, but if anyone had some small chances later it was Kamsky.
More updates to come, to this post!
Update #1:
We have a few more moves: after 19.Nf4, there's 19...g5 20.Nh5+ Kg8 21.h4 h6 22.hxg5 hxg5 23.Rf3 and now Anand is thinking. Black is still okay, as far as I can tell, but it's starting to get tricky. For instance, after 23...Bb7 White can try 24.Nxf6+ Qxf6 25.e5 Qxe5 26.Re1 Qf6 27.Re6, when Black's best is to scurry into a nearly equal ending with 27...Bxf3 28.Rxf6 Rxf6 29.gxf3 Rd8 30.Qg5+ Kf7.
Update #2:
After thinking for about 26 minutes in the position above, Anand played 23...Kf7?. This loses: 24.Nxf6!! Kxf6 25.Rh3 Rg8 26.Rh6+ Kf7 27.Rh7+ (aiming to follow with Rcc7) 27...Rg7 28.Rxg7+ followed by either 29.Qxg5+ or 29.Rc7+, depending on which way Black recaptures. Or if 24...Qxf6 25.Rh3 and White floods in with Rc7+, Rhh7, Qb4, Bc4+ and so on. If Topalov plays 24.Nxf6, the game is probably over.
Update #3:
Topalov just took a few minutes to play 24.Nxf6, and Anand sank back into a misery-filled thought. After 25 minutes, he chose 24...Kxf6, and Topalov quickly played 25.Rh3. Black's position is hopeless, and the only question is how long Anand can keep the game going, to make Topalov work a little and to perhaps reduce the game's publishability for posterity.
Update #4:
Anand did what he could, but the position was hopeless. The game ended after the moves 25...Rg8 26.Rh6+ Kf7 27.Rh7+ Ke8 28.Rcc7 Kd8 29.Bb5! Qxe4 30.Rxc8+ 1-0. It was a very easy win for Topalov, and probably amounted to little more than Topalov remembering his homework and Anand forgetting his.
Stay tuned for a fuller analysis with a replayable board.