MousePressed Bg change - OpenProcessing

mySketch
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// only 1 "=" means we are telling the program that this is the state of the boolean when we 
// begin the program. So here, the screen is blue, NOT YELLOW, when we run it. 
​
boolean backgroundisYellow = false; // when program starts, background is not yellow  
  
void setup(){
  size (500, 500);
}
​
void draw (){
  // Two "==" mean it's checking if this statement is true or false.
  if (backgroundisYellow == true){         // Checks if background is yellow
    background (255, 255, 0);              // if that is true, then background is yellow
  } else {                                 // Checks if background is NOT Yellow
    background (0, 255, 255);              // changes it to blue
  }
  
}
​
void mousePressed(){                      // When mouse is pressed
  if (backgroundisYellow == true){        // checks if background is yellow, i.e. if the boolean is true
    backgroundisYellow = false;           // if it is true, then when we press mouse change the boolean to false, 
                                          // i.e. make it blue now!
 // without the "else" statement, the background will only change once. It wont switch back and forth   
 } else {                                 // When we press mouse, change boolean to true
    backgroundisYellow = true;            // i.e. change it to yellow now!
 }
}