Just when your kid goes into meltdown mode, and you're about to lose your marbles, Shelburne-based WinWin Apps produces a slick new application that uses marbles — images of them, anyway — to help. The Marble Jar is a tech-savvy twist on the old-school concept of dropping marbles into a canning jar to mark progress toward a goal. But this iPod and smartphone app is more than just an elaborate sticker chart, says WinWin owner Anna Palmer. The Marble Jar idea is to envision an outcome — friendlier, more cooperative behavior, for instance — and then define the actions your family needs to take to get there. Each step toward the goal earns a colorful virtual marble that, when tapped, plinks melodiously into the jar. Create multiple jars and carry them all in your pocket at once, instantly rewarding behavior that earns an aggie. Don't think of it as technology supplanting parenting, though. Use the app to start family conversations about your goals. And invite everyone to help plan the celebration you'll have when the jar is full. That way you'll be working — and celebrating — together.