GameStop says it’s selling up to 3.5 million of its shares, a move that will allow the video-game retailer to take advantage of the big surge in its stock price this year. The company said the shares will be sold through an “at-the-market” offering, which lets a publicly traded company raise capital over time by offering securities into the already existing trading market. GameStop plans to use proceeds for general corporate purposes, to further strengthen its balance sheet and to speed up its transformation process.