Simple check valve
simple check-valve on A
Drag mouse to rotate
Drag mouse with shift pressed to zoom
Drag mouse with shift pressed to zoom
simple check-valve on B
Drag mouse to rotate
Drag mouse with shift pressed to zoom
Drag mouse with shift pressed to zoom
simple check-valve on AB
Drag mouse to rotate
Drag mouse with shift pressed to zoom
Drag mouse with shift pressed to zoom
simple check-valve on P
Drag mouse to rotate
Drag mouse with shift pressed to zoom
Drag mouse with shift pressed to zoom
simple check-valve on T
Drag mouse to rotate
Drag mouse with shift pressed to zoom
Drag mouse with shift pressed to zoom
