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 and a pre-selected algebraic result, the base image having a pre-selected base image reference point, and the overlay image having a plurality of numbers, 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; and in response to alignment of two or more numbers from the grid on the base image reference point, the two or more numbers equalling the algebraic result when one or more algebraic operator is applied to the numbers, indicating positive authentication.