On behalf of the McDonald's Owners of Chicagoland and Northwest Indiana, Leo Burnett's a.m. sales-radiating sundial, across from Wrigley Field, is part of an ongoing breakfast campaign intended "to showcase McDonald's offerings throughout different times of the morning," says CD/AD Vince Cook. "The shadow's progression, from early riser to late sleeper, spans the morning menu and gives each item a literal moment in the sun. At noon, the dial forms a perfect McDonald's M." The rest of the day doesn't figure in this solar branding exercise, but this half-a-day idea differentiates it from traditional sundials, says engineer Christian Huff of Edex Inc., whose services were required for what Cook calls "harnessing the power of the world's first alarm clock." Huff says not only is this the only "abbreviated" sundial he's seen, but he points out that the billboard has a limited life span based on the sun's position. "As summer ends, the movement of the sun will shorten the shadow