The driver steps on yellow pedals to make blue cranks rotate thanks to 4-bar linkages of pink conrods.
Gear drives of blue gear (fixed to the blue crank) and violet gear (fixed to the rear shaft) are for increasing speed of rear wheel.
The rear wheel is fixed to the rear shaft.
Here the use of a freewheel is not suitable. It may causes complications in starting to get forward motion of the bike. However it is not comfortable for driver when the bike moves thanks to its inertia.
This video was made based on video:
/watch?v=1gFtIyjnFAA