This page is the tl;dr video clip introduction to “mirror concepts”. The slightly-more-detailed writing intended for other Aikido instructors who want to pursue progressive training methods can be found here. The e-book we released back in 2000 is available at the author’s discretion to select people who may request it.
This is a VERY short clip showing one of the clearest and simplest examples of “mirrored” methods.
This video is a demonstration of the same relationship between ikkyo and kokyunage, with “male triangle” body movement. It is presented first by showing the techniques serially, then by overlaying video clips with progressive transparency, showing just how identical the correct movement might be.