A user interface suited for use on mobile devices for entering characters which may require one or more modifiers is disclosed. The interface may be implemented utilizing a touch screen interface on which a user engages the interface, is provided feedback, and removes the user's touch to enter a character. The interface presents a series of main, supplemental and modifier keys. Touching an interface button or main key presents a series of “petals” or supplemental keys emanating from the main key. Each petal or supplemental key may in turn present one or more sub petals or modifier keys emanating from the supplemental key. Each petal or sub-petal may represent another character or a modifier action. The characters and/or actions on the supplemental keys and modifier keys provide options for characters or modifiers which are dependent or related to the main input key.