Spiral following an outline inside a closed curve

 From:  sunspeed
12030.1 
Hi,

I am looking for an efficient way to create a spiral that follows the inner outline of a closed curve with a defined distance between the lines.

For example, starting from the upper-left corner of a rectangle, the spiral would follow the shape’s interior outline, continuing inward turn by turn at a specific offset distance.

Could you suggest a method or tool to achieve this?

Thanks,
Joerg