For a true to form N-back game take a look at Brain Workshop.
Features:
-13 game modes, one of which is the N-back matching operation
-dynamic difficulty adjustment (you sit at the same screen from level 1 to N)
-61 stimuli across 10 themes
----audio/image/text data types
----1-4 simultaneously
----each stimulus is a continuum where < > = can be assessed
-4 time-paces, slow/medium/fast/variable i.e. user-driven
-three ways to play
----with boxes for each chunk (N chunks on screen)
----with boxes for each chunk and a box for the helper at the top of the screen (the helper is a chunk mixed in to
more finely adjust difficulty) (N chunks + 1 on screen)
----"classic n-back" with no boxes, no helper, and a number for N
-configurable beat gives you control of the mood
-configurable user profile
----can choose color scheme
----options for audio/visual feedback
----options for stimulus movement/scaling
----can slow&deepen and quicken&squeakin voice/instruments to your liking (my voice work is amateur, improvements are coming)
----more (taking suggestions and contributions!)
-two sets of scores, one with the helper, one without
-time played tracked, graphed...get green if you know what I mean
-supports mouse/keyboard/gamepad
-stereo features
