Shares of Zynga Inc. /zigman2/quotes/209662259/composite ZNGA -6.07% are up 12.9% in midday trading Thursday and on track for their biggest single-day percentage gain since 2014 if the gains hold through the close. The stock rose 23.6% on Jan. 31, 2014. Zynga's rally comes after the mobile-games maker beat earnings expectations the prior afternoon. Wedbush analyst Michael Pachter called it a "near perfect" fourth quarter for Zynga and reiterated his outperform rating on the stock. Jefferies analyst Alex Giaimo wrote that "despite increased investor caution heading into the print, Zynga posted impressive 4Q results and a safe [fiscal-year] guide that should help pull the stock out of the penalty box." He has a buy rating on the stock. The stock surge Thursday helped Zynga's stock crawl out of the red on a one-month and three-month basis. Shares have risen 6.7% over the past month and 6.4% over three, as the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.94% has posted respective gains of 2.9% and 8.6% over those spans.