We describe a technique that supports the previewing of navigation, exploration, and editing operations by providing convenient Undo for unsuccessful and/or undesirable actions on multilevel input devices such as touch screens and pen-based computers. By adding a Glimpse state to traditional three-state pressure sensitive input devices, users are able to preview the effects of their editing without committing to them. From this Glimpse state, users can undo their action as easily as they can commit to it, making Glimpse most appropriate for systems in which the user is likely to try out many variations of an edit before finding the right one. Exploration is encouraged as the cumbersome returning to a menu or keyboard to issue an Undo command is eliminated. Glimpse has the added benefits that the negative effects of inconsistencies in the Undo feature within an application are reduced.