Online gaming company Zynga says it is abandoning plans for real-money gambling in the United States, an announcement that saw its stock fall 14 percent. Investors reacted badly to the word Zynga was giving up its long-running efforts to build a real-money gaming business, once considered a vital revenue source for the firm. Zynga had hoped to tap into a potentially lucrative new revenue stream by launching real-money casino games around the world and launched a pilot effort this year in Britain, where such games are highly regulated. \"While the company continues to evaluate its real-money gaming products in the United Kingdom test, Zynga is making the focused choice not to pursue a license for real-money gaming in the United States,\" the company said in a release. Zynga has seen its mobile gaming audience shrinking under competition from aggressive rivals; its daily active users dropped 45 percent from its all-time peak last year of 72 million to 39 million, Mashable reported Thursday. Earlier this month Zynga replaced Chief Executive Officer Mark Pincus with Don Mattrick, who had been the president of the interactive entertainment group at Microsoft.