2) Corrected the Java simulation to allow units (or to ask for the answer in mm) and to prevent the vernier scale from being unreadable.

added mm in texts
made xmagnify = -10 , ymagnify = 0
found that mx and my is causing the weird behavior, made them -10 and 0 as well like xmagnify and ymagnify so that it loads at the centre of the simulation view!

the simulation is downloadable from the this post or
mirror here