Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...Bc5/5. Nxf7/5...Bxf2/6. Kxf2/6...Nxe4/7. Ke3/7...Qh4/8. g3/8...Nxg3/9. hxg3/9...Qd4/10. Kf3/10...O-O/11. Rh4/11...e4

11...e4
After Kg2, Black can finally capture with Qxc4 and the Traxler Counterattack is proved to have merit. Black has an obvious attack on the White king but White can finally start developing their pieces, starting with moving their f7 knight back.

Finally, it should be noted that 12. Rxe4 is a mistake because after 12...Ne5+ 13. Rxe5 Qxc4, White has no way to defend their knight.