7. No Modes
A Gesture is an action (a keystroke, a mouse move) expected to result in some effect (a letter being added to a document, a cursor moving).
A mode changes the effects associated with some or all gestures. caps lock is a mode. “apps” are modes. Modes are bad if they result in modal error: the unawareness that a mode has been activated, resulting in unexpected effects, and possibly unawareness it *is* a mode, or how to get out of it. VIM is prime offender. so are modern TVs.
modes are typically employed as solutions to the situation of the number of functions in a system far exceeding the number of available external controls. this can happen either as a result of featuritis, or an apple-esque fetish for small numbers of buttons.
suggested remedies include quasimodes like the shift key, that activate a mode only while a button is being held down. another approach is developing composable UI conventions like GUI menus, or search, that can scale without modes.