Input: pink coulisse.
End point of green slider traces a parallelogram (in green)
Length of horizontal side = length of grey runway – length of blue slider
Length of vertical side = length of blue runway – length of green slider
Parallelogram angle = angle between grey runway and blue runway (90 deg. for this case).
Rotary axis of the pink coulisse is at intersection of the parallelogram diagonals.
The mechanism has two DoFs. Violet spring always forces blue slider or green slider towards the ends of grey runway or blue runway.