Around this time Larsen diversified his style, switching over to risky and unusual openings in some of his games, to try to throw his opponents off balance; this led to the recovery of his form and further development of his chess. He finished 2nd at the 1963 Halle Zonal with 13/19, behind winner Lajos Portisch, to advance to the Interzonal the next year. At Belgrade 1964, he shared 5th–6th places with 10/17 (Boris Spassky won). He tied for 5th–7th places at Beverwijk 1964 on 9½/15; Keres and Nei won. Larsen's unusual openings were on full display at the 1964 Amsterdam Interzonal, where he shared the 1st–4th places on 17/23 with Boris Spassky, Tal, and Vasily Smyslov, advancing as a Candidate.