Stylus based text input using expanding CIRRIN

CIRRIN [3] is a stylus based text input technique for mobile devices with a touch sensitive display. In this paper we explore the benefit of expanding the letters of CIRRIN to reduce the overall difficulty of selecting a letter. We adapted the existing CIRRIN to expand the characters as the stylus approached it to create a new text entry technique called expanding CIRRIN. In a small user study we compared the standard CIRRIN and expanding CIRRIN for different sentences. Our results indicate that expanding CIRRIN increases error rates and text input times. We observed that expanding the letters often made the stylus enter the CIRRIN ring adjacent to the intended letter, thereby increasing error rates. We discuss the implications of these results, and possible applications of expanding targets with other text input techniques such as the Metropolis [7] soft keyboard.