Facebook launched a widget for developers to entice first-time buyers during the middle of game play.

When developers implement this new widget, only users who haven’t previously paid for virtual goods will see in-game icons promoting the offer.

Today’s announcement builds on a promotion announced last month, in which users who have never paid for Facebook games or elements within them get $4 worth of Credits or other in-game currency free after buying the first $1 — and the social network foots the bill for the freebie.

Facebook Engineer Pratap Pv said in a post on the developer blog, “Early data shows that about 20 percent of the users who make that first-time purchase come back to spend more within a month.”

Facebook recommended that developers opt to offer their own in-game currency for the promotion; that will ensure that users spend the digital coinage within the developers’ own games. (Giving away Credits lets players redeem the promotion in any developer’s app.)

Users can pay via credit card or PayPal.