I plan to make a mirror which can change the image to bigger or smaller , if  your body leans towards  to it  or leans away.

here’s some inspiration

I will use distance sensor , pvc mirror soft material , syringes piston and servo motor

here’s how concave mirror and convex mirror work

http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/mirray.html

and I have to make some experiments to choose a better curvature arrange of the mirror surface

(pictures from JEFF KOONS)