By default, p5 runs in Global Mode, which means that all p5 functions are in the global scope, and all canvas-related functions apply to a single canvas. p5 can also run in Instance Mode, in which those same functions are methods of an instance of the p5 class. Each instance of p5 may have its own canvas.
To use instance mode, a function must be defined with a parameter representing the p5 instance (labeled p in this example). All the p5 functions and variables that are typically global will belong to this parameter within this function’s scope. Passing the function into the p5 constructor, runs it.
