23. The method of claim 21 , further comprising: while presenting the secondary key plane of the virtual keyboard, receiving a second user input invoking the shift key on the secondary key plane; and upon receiving the second user input, presenting the primary key plane of the virtual keyboard in place of the secondary key plane.
21. The method of claim 14 , wherein the primary and the secondary key planes each includes a shift key that is operable to trigger key plane switching in the virtual keyboard between the primary and the secondary key planes when invoked by user input.