An apparatus, comprising: at least one computer processor; and at least one non-transitory computer memory coupled to the at least one processor, the at least one non-transitory computer memory having computer-executable instructions stored thereon that, when executed by the at least one processor, cause the at least one processor to: generate an interactive graphical user interface including: two or more letter selection buttons arranged in a row of letter selection buttons on the interactive graphical user interface, wherein each letter selection button of the two or more letter selection buttons is assigned a letter pair; and one or more intervening buttons collinear with and overlapping the row of letter selection buttons, wherein individual letter selection buttons and individual intervening buttons are offset from one another, and wherein each of the one or more intervening buttons is assigned one letter; record (510, 512) an actuation of a letter selection button of the two or more letter selection buttons as a selection of the letter pair assigned to the actuated letter selection button; and record (510, 512) an actuation of an intervening button of the one or more intervening buttons as a selection of the letter pair assigned to a letter selection button overlapped by the actuated intervening button. at least one computer processor; and at least one non-transitory computer memory coupled to the at least one processor, the at least one non-transitory computer memory having computer-executable instructions stored thereon that, when executed by the at least one processor, cause the at least one processor to: generate an interactive graphical user interface including: two or more letter selection buttons arranged in a row of letter selection buttons on the interactive graphical user interface, wherein each letter selection button of the two or more letter selection buttons is assigned a letter pair; and one or more intervening buttons collinear with and overlapping the row of letter selection buttons, wherein individual letter selection buttons and individual intervening buttons are offset from one another, and wherein each of the one or more intervening buttons is assigned one letter; record (510, 512) an actuation of a letter selection button of the two or more letter selection buttons as a selection of the letter pair assigned to the actuated letter selection button; and record (510, 512) an actuation of an intervening button of the one or more intervening buttons as a selection of the letter pair assigned to a letter selection button overlapped by the actuated intervening button. generate an interactive graphical user interface including: two or more letter selection buttons arranged in a row of letter selection buttons on the interactive graphical user interface, wherein each letter selection button of the two or more letter selection buttons is assigned a letter pair; and one or more intervening buttons collinear with and overlapping the row of letter selection buttons, wherein individual letter selection buttons and individual intervening buttons are offset from one another, and wherein each of the one or more intervening buttons is assigned one letter; two or more letter selection buttons arranged in a row of letter selection buttons on the interactive graphical user interface, wherein each letter selection button of the two or more letter selection buttons is assigned a letter pair; and one or more intervening buttons collinear with and overlapping the row of letter selection buttons, wherein individual letter selection buttons and individual intervening buttons are offset from one another, and wherein each of the one or more intervening buttons is assigned one letter; record (510, 512) an actuation of a letter selection button of the two or more letter selection buttons as a selection of the letter pair assigned to the actuated letter selection button; and record (510, 512) an actuation of an intervening button of the one or more intervening buttons as a selection of the letter pair assigned to a letter selection button overlapped by the actuated intervening button.