1. A computer-implemented method for an application development tool, the method comprising: receiving, by processing logic of a computer running the application development tool, user input pertaining to a plurality of variables associated with a multivariable function of an application, wherein the multivariable function defines a behavior of the application and defines a relationship between an input device and an output device selected for the application; and causing code for the function to be automatically generated to update the plurality of variables based on the user input.