Sometimes you try to switch the state of the game quickly to let the player “flow” fast and easily through it (people playing mobile games sometimes don’t have a lot of patience). Imagine in a puzzle game, when the player finishes a level, you drop her immediately in the next one. But what happens when you do it really fast, and the levels are similar? Many players will not understand that a state change has occurred, and will think that you just reversed their last move, or that they are still in the same. Stating that a puzzle was finished does not make it explicit that you are now showing something different. Additional cues are sometimes required. Sound cues alone are not good enough, as people might play with sound off or on noisy places. Text, fade in/outs, etc. or other visual cues seem to work best.