By Mike Isaac and Kellen Browning, The New York Times SAN FRANCISCO — For years, Christian Lantz has played “S.T.A.L.K.E.R.,” a first-person shooter video game set in a post-apocalyptic Ukraine that became a cult hit for its immersive role playing. So when Lantz, an 18-year-old high school student, heard that a sequel was coming this year, he knew he had to buy it. That was until GSC Game World, the Ukrainian company behind the computer game, announced last month that the new “S.T.A.L.K.E.R.” would incorporate the crypto-based assets known as nonfungible tokens, or NFTs.