There is a brief video that includes an interview with Susanne Jaeggi
and Martin Buschkuehl that people here might find interesting:
http://www.sciencentral.com/video/2008/12/31/brain-boot-camp-makes-you-smarter/
They show a few clips of people playing the BrainTwister game, and I
tried to see if there was any kind of feedback after each turn. The
screen showed only the squares in the grid in the brief clips that I
saw and nothing else at all (no text). It may give some kind of
feedback when a wrong answer occurs and there just weren't any wrong
answers in the brief clips they showed, but there is definitely no
other text on the screen ordinarily (e.g., there is no countdown
giving the number of remaining items like BW shows when you have
feedback enabled). One other thing I noticed was that the colors BT
uses are blue on a solid black background (BW has a config option for
black background, too), and the black background fills the entire
screen, so you see nothing except an entirely black screen with very
large blue squares (and a tiny dot or cross in the center of the
screen). In particular, there are no gridlines like BW has.
If anybody in this group has actually played Brain Twister, please let
us know if it gives feedback after wrong answers.