The line between unsound and stupid
There's a small group at chess dot com devoted to the 1. d4 Nf6 2. g4 gambit, where a couple of European players shared some very nice games. My kind of folk, so I joined them, though it smacks of the "guild dinkiness" that I railed against as a gaming forum host decades ago.
Since there's not much activity at the Gibbins-Weidenhagen group, my new friends invited me to join the Unsound Openers, where my old friend Albert Rich takes part, so I joined the bigger guild of dinks. The hazing ritual is sharing one's favorite unsound opening — mine is 1. e4 c5 2. b4 cxb4 3. a3 d5 4. exd5 Qxd5 5. Nf3 e5 6. axb4 Bxb4 7. Ra3, I said.
Weeks pass, and a newcomer says his favorite is 1. e4 e5 2. f4 exf4 3. Kf2.
There's a line between unsound and fatuous, and the Tumbleweed Gambit crosses it.
One thing people don't understand about the PurdyFine approach to the opening is that it's based in position. My favorite 1. d4 Nf6 2. g4 is doubly-rooted in position play — in the opening, it's designed to deflect Black from the center; in the middlegame, it's designed to give play to the rooks. The aforementioned exchange sacrifice in the Sicilian Wing Gambit has a positional basis: The queen rook isn't doing much, so 7. Ra3 intends to swing the rook to b3, d3, or e3 — all of which make a threat. If Black accepts the rook with 7....Bxa3, then 8. Bxa3 recaptures with a developing move and prevents Black from castling, followed by Nb1-c3 to hit the queen plus Nc3-b5 to hit the black squares that aren't covered by the dead bishop.
The King's Gambit is positionally-motivated. 1. e4 e5 2. f4 exf4 deflects Black from the center. Then White's goals are to fill up the center while recovering the f4-pawn, resulting in an open file for the middlegame. However, White has the immediate concern 3...Qh4+, which uproots the white king because 4. g3 is a relatively useless interposition, so 3. Nf3 is the most common and natural move, when Black has many ways to go.
One of the best ways is 3...d5, reducing White's center. Many players try to take that resource away from Black by playing 3. Bc4 or 3. Nc3. Fischer and Polgar preferred 3. Bc4, which restrains ...d7-d5, and gives the king a flight square: 3...Qh4+ 4. Kf1. Steinitz and Keres tried 3. Nc3, which controls d5 with knight before bishop. 3. d4 also deserves a go. After 3...Qh4+ 4. Ke2, an interesting game is in store.
3. Kf2? is just stupid (or contemptuous), doing nothing to achieve White's aims of occupying the center and opening the f-file. White is hoping to exploit Black's greed — for example, 3...Qh4+ 4. g3 fxg3+ 5. Kg2 gxh2 6. Rxh2 Qxe4+ 7. Nf3 d6 8. Kg1 Be6 9. Nc3 Qg4+ 10. Rg2 with active play. But any sensible player with Black is just going to play 3...d5.