NEW YORK (AP) — Shares of online game company Zynga Inc. fell Wednesday after a key executive, its chief creative officer, said he was leaving to start a new company.

THE SPARK: "Being at Zynga in the early days reminded me of how much I love being an entrepreneur," the executive, Mike Verdu, wrote in a company blog post late Tuesday. "After a lot of soul-searching, I have decided to go back to my roots and start a new company."

His departure follows that of John Schappert, the company's chief operating officer, earlier this month. He was at Zynga for less than a year and a half.

THE BIG PICTURE: Zynga's games, such as "FarmVille" and "Mafia Wars," are played mostly on Facebook. The company has struggled has struggled since going public in December due to the sharp drop-off in users of its most profitable games, delays in developing new games, the growing pull of Facebook's mobile app and because Facebook has changed the way it promotes games.

Zynga's mobile games, such as "Words With Friends," are popular but don't make as much money as the Facebook versions. Facebook makes up nearly all of Zynga's revenue.

The San Francisco company recently reported dismal second-quarter earnings and cut its guidance for 2012.

THE SHARES: Zynga shares fell 8 cents, or 2.6 percent, to $3 in light afternoon trading. Shares have dropped 70 percent from the company's initial public stock offering price of $10.