I find I'm just getting used to the accumulated smudges on my iPad screen, and no longer obsessively wipe it clean. Now, I see that this represents a map of the iOS UI! (Remnants of a Disappearing UI: Design Language News)!  As it turns out, each app generates its own pattern of finger-smears, which is actually quite interesting from the perspective of UI design.  So for example, the mail app generates a very different pattern than, say, Safari use - and interestingly the article implicates personal usage patterns relating to how the iPad is held - portrait vs landscape.  The video app only has two fingertip smudges! Which all brings to mind a game I bought for the iPad the other day.  I was intrigued by Papa Sangre, a game with virtually no visuals, in which you navigate in pitch dark using binaural sound effects, in an effort to rescue a lost soul.  It's genuinely quite creepy, but you no need to have decent headphones, a reasonably quiet environment and not too many visual distractions.  Time will tell whether it's fun enough to keep my attention (I don't play too many games on computers or the iPad as a rule). The minimal graphics in Papa Sangre would undoubtedly generate a limited 'heat map': one only uses finger-swipes to orient oneself relative to the soundscape, then finger taps to regulate one's speed in the labyrinth.  And you can trip over your own feet!