Four Knights Game:Halloween Gambit

A wild knight sacrifice on e5: White gives a piece for a big pawn centre and a quick attack. The name refers to the scare it gives unprepared opponents.

It is reached after 7 moves: 1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Nxe5. It is a line of the Four Knights Game.

Black is to move and has 30 legal moves. Over the next four moves — two for each side — the game can branch into 1,240,756 different games. Those games reach 428,640 different positions: most positions can be reached in more than one way, 2.9 on average.

The Lichess opening list names 2 further lines after this position, such as Oldtimer Variation (4... Nxe5 5. d4 Ng6 6. e5 Ng8 7. Bc4 Bb4 8. Qf3 f5) and Plasma Variation (4... Nxe5 5. d4 Nc6 6. d5 Ne5 7. f4 Ng6 8. e5 Ng8 9. d6 cxd6 10. exd6 Qf6 11. Nb5 Rb8).

The same moves can be played in 56 different legal orders that all reach this position. For example 1. Nf3 e5 2. e4 Nc6 3. Nc3 Nf6 4. Nxe5, which starts as the Zukertort Opening.