The first thing I thought of while reading your comment were graphical adventure games, where you pretty much had to click on everything to see what did somethi

The first thing I thought of while reading your comment were graphical adventure games, where you pretty much had to click on everything to see what did something. The fundamental difference with modern user interfaces is that you now have to tap, drag your finger across the screen in different directions, drag both fingers across the screen in different directions, pinch, unpinch, and whatever other gestures seem to be relevant to the situation. For good measure, try gestures that don't seem to be relevant either because the software may surprise you! Now I know that a lot of these user interface decisions do offer value, but they are only valuable if you know that they exist.