Revised version at HCIL-2007-14
In this paper, we present ThumbSpace, a software-based interaction technique that supports one-handed thumb op-eration of touchscreen-based mobile devices. Our goals are to provide accurate selection of all interface objects, espe-cially small and far targets, which are traditionally difficult to interact with using the thumb. ThumbSpace is designed to provide these benefits independent of the application design. This can free designers to focus on effective presen-tation, as well as efficient interaction when two hands and a stylus are available. We present design tradeoffs we en-countered and a comparative evaluation of ThumbSpace against peripheral hardware (indirect) and touchscreen (di-rect) input methods for object selection during standing and walking activities. Although ThumbSpace and another new finger-based touchscreen technique, Shift, were less accu-rate than the directional pad, they were preferred, in combi-nation, to all other methods studied for interacting with 2D interfaces and small (3.6 mm) targets.