Slindow is a language inspired by this cops and robbers challenge. However, unlike the linked challenge (based on 3 consecutive items), this only involves two consequtive items, which simplifies the programming.
Slindow processes in digraphs (aka 2 consequtive characters). Due to a bug that I'm too lazy to fix (anyway ...
><>, 39 bytes, safe
Try it online!
Works in ><>, Gol><>, somehow not *><>, and Backhand.
vdv Push the speed down twice
II Take 2 inputs
$$$$$$$$$>r A bunch of stuff that do nothing
n; More ...