Customising Processing in a PApplet

I'm basically creating a music player and thus far I have a PApplet that plays music that reacts with visual art; it also encompasses a pause and play button that pauses and plays the animation and music when pressed. What I'm now currently trying to do is to create a button that when pressed, changes the number of rectangles drawn on my screen. I've tried changing the sketch.init from (7,7) to (10,10) in the if else statement for the mouse event but it just crashes every time. Any help would be much appreciated.