Palm, maker of the Treo line of smartphones, has hired former Apple employee and Silicon Valley software designer Paul Mercer to help the company respond to the iPhone. The New York Times reports that Mercer began work three weeks ago at Palm on a line of new products. Mercer joined Palm from Inventor, an independent design firm that he headed in Palo Alto, California. He joined Apple in 1987, working as the lead designer of the Macintosh finder. Mercer later founded Pixo, a mobile software firm that created the basis for the iPod interface. More recently, he helped design the Samsung Z5 digital audio device.