1. One or more computer readable media having computer readable instructions stored thereon that when executed by a processor implement a method of authenticating a user of a computing device, the computing device having a memory storing a base image and an overlay image, the base image having a pre-selected base image reference point, and the overlay image having a pre-selected overlay image reference point, the method comprising: generating a modified base image; generating a modified overlay image; displaying, on a display, the modified base image overlaid by the modified overlay image; receiving an input for moving one of the modified base image and the modified overlay image; moving the one of the modified base image and the modified overlay image in response to the input; detecting a selection of a color for a portion of the display; and in response to alignment of the base image reference point on the modified base image with the overlay image reference point on the modified overlay image at a point on the display and the selected color matching a pre-selected color, indicating positive authentication.