Every two minutes its 220, 000 giant glass mirrors, lined up in perfect rows, rotate imperceptibly with a barely audible click, tracking the sun's path across the sky.
To be sure, cookie technology does not prove perfect causality, but it provides a lot more transparency than simply tracking "click-through rates"--or running a print ad in a newspaper or magazine.
When we flicked the mouse on it was easy enough to spot it over Bluetooth on our regular Mac, but it only worked with tracking and single click -- none of this capacitive nonsense without a software update, naturally.