iA on responsive type (graded fonts)
The typeface [in the screenshots] is iABC, an in house production that comes in different grades depending on the resolution of the screen (aka responsive typography).
If you’re curious about how grade adjustments can change the feel of a typeface, look no further. iA are also the folks behind iA Writer, the iOS and Mac app. Oliver posted screenshots of the app’s custom typeface, Nitti Light (used on iPad 1 and 2), for comparison with Nitti Light HD (to be used on the new Retina display iPad).