Physical buttons provide rich force characteristics during the travel range, which are commonly described in the form of force-displacement curves. These force characteristics play an important role in the users' experiences while pressing a button. However, due to lack of proper tools to dynamically render various force-displacement curves, little literature has tried iterative button design improvement. This paper presents Button Simulator, a low-cost 3D printed physical button capable of displaying any force-displacement curves, with limited average error offset around .034 N. By reading the force-displacement curves of existing push-buttons, we can easily replicate the force characteristics from any buttons onto our Button Simulator. One can even go beyond existing buttons and design non-existent ones as the form of arbitrary force-displacement curves; then use Button Simulator to render the sensation. This project will be open-sourced and the implementation details will be released. Our system can be a useful tool for future researchers, designers, and makers to investigate rich and dynamic button"s force design.