A computer-implemented method for controlling access to a computing device entails displaying a user-rotatable three-dimensionally rendered object on a display of the computing device, the object presenting a plurality of user-selectable visual indicia such that only a subset of the indicia are visible at any one angle of rotation and providing access to the computing device based on user input received in relation to at least one of the visual indicia. The object may be spherical or polyhedral or it may be composed of a plurality of independently rotatable rings that together form a generally spherical shape. The visual indicia may be letters, numbers, symbols, colours, photographs or any other visually distinctive indication.