HELP! How can I use 'Arc-like curve' as a Goalobject in Kangaroo2 ?

Newbie, I'm building a kinematic door simulation with multiple joints.

I thought I can use Kangaroo for my project as Daniel presented; with line segment.

So I tried it with controllable Arc curve as follows, (I wish I can control curves in Rhino and Grasshopper simultaneously. I mean, real-time monitoring with this simulation..)

But it does not work as my way of thinking. When I use Length(line) component in Kangaroo2, it generate only straight lines, not Arc curve(like above Rhino view).

Does anyone have a idea? Should I approach this totally different way?

Thanks.

-Jae-