A real-time stream of position, sound and colour cues plays one step at a time, flag the channel whenever the current cue matches the one N steps back.
Cues arrive on a fixed beat: a cell lights on a 3×3 grid, a tone plays, and a colour shows. Your job is to flag a channel the moment its current cue repeats the one from N steps earlier. Correct flags disarm wires; clear a round cleanly and N rises on its own, making the memory load deeper. Too many misses and the timer wins.
Backtrack is a brain trainer built on the well-known N-back working-memory task, exercising the mind's mental scratchpad.
Flagging a cue when it matches the one from N steps earlier is the n-back task, introduced by Wayne Kirchner in 1958 and now a standard assessment of working memory in psychology and cognitive neuroscience.
Running three channels at once — position, tone and colour — is the multiple-n-back variant, and raising N automatically on a clean round is the adaptive staircase the research versions use.
One honest note, since the genre often overstates it: n-back training is purported to raise working-memory capacity and fluid intelligence, and while some studies have found such a transfer, others have not. It is a well-defined measure of a real capacity; whether practising it makes you generally smarter is unsettled.
Backtrack is an original free browser brain trainer built on the well-known N-back working-memory task, wrapped in a bomb-defusal frame with adaptive difficulty. Made in-house for PlayPendium.