how can i set up a wall in the task

Hi Yihui, I'm not sure what you mean by a soft wall. I wouldn't recommend making a wall that is always 50 N as someone's hand getting hit suddenly with 50 N is quite a kick. What is usually done is to build a restoring force that increases as you move further into the wall. An example is the force channel task (which is just two force walls, one on either side of the channel). https://kinarm.com/download/force-channel-demo/ The restoring force is calculated in the Calculate force channel function inside the Force Channel subsystem. The function defines the channel as a line between two points (x1, y1) and (x2, y2) and calculates the distance of the hand to that line and applies a restoring force that is a sum of a restoring spring force -(wallStiffness)*x and a viscous force that is included to dampen oscillations.   Let me know if you have any questions. Cheers, Koloman