Restricting line drawing to a single environment

[Zachary Luppen]

Hello,

I'm part of a group designing an application for an augmented reality sandbox. The way it works, a user designates the speed and direction of a particle in a 2d potentials contour map, and upon hitting a "Go!" button, a separate algorithm reads in a text file the app will output to, performs the calculations, and then animates the particle. The app has been designed using MIT App Inventor 2, and we are now redesigning it in Kivy, which we are all very new to. We're currently stuck on designating the environment in which the particle speed and direction parameters can be drawn. As it stands, the user is able to draw vectors across the entire app, but we would like this restricted to the environment on the left side of the app. The sliders on the right side will be used to adjust the vector, but don't communicate with the vector yet. Angle corresponds to the the direction and speed corresponds to the length of the vector. However, when a user moves a slider icon, the vector follows the user's touch, which we also don't want it to do. How could we go about fixing these issues? Pictures and code attached.

Thanks!