If you have a 2-state system, the current state and what will happen next are complementary. In other words, one may assume that the two pieces of information (state and what happens next) could be conveyed through a single control — a switch-state button. That’s because, if users knew one they could infer the other. However, this can require time and cognitive effort from the user. There are two alternative methods to use a single control to indicate both state and what will happen next:

• The button label communicates the state that the system will move to
• The button communicates the active state using a shadow