code to create a "start screen" - you can build off this to make multliple screens/stages in a sketch.

Modulo Example w start screen.pde

// Modulo Example w start screen
// Steve Lambert March 8, 2017 
// v0.1


// initializing variables
int interval; // how often changes
int xPos;
int yPos;
int circleW = 50;
int stage = 0;

// FONT SETUP
PFont LeagueGothicBig;
PFont LeagueGothicSmall;
int fSizeBig = 34; // size of big font
int fSizeSml = 24; // size of small font
int textHeight = height/2;
String line1 = "PRESS ENTER TO START";

void setup() {
  size(600,600);
  smooth();
  noStroke();
  background(255);

  LeagueGothicBig = createFont("LeagueGothic-Regular", fSizeBig, true);
  LeagueGothicSmall = createFont("LeagueGothic-Regular", fSizeSml, true);
} // end setup

void draw(){
  background(255);
  if (stage == 0){
    startScreen();
  } else if (stage == 1) {
    moduloSketch(); 
  }
}

void keyReleased() {
  if (key == RETURN || key == ENTER) {
    println("Hit Return stage 0");
      if (stage == 0){ // if on the start screen
        stage = 1;   // advance to the next stage
      } else { // otherwise do nothing

      } // end else
  } // end CODED
  else if (key == '0') { // if it's not coded, and it's 0
    stage = 0;         // reset
  }
    
}

void startScreen() {
  fill(255);
  background(255, 0, 0);
  textAlign(CENTER, CENTER); 
  textFont(LeagueGothicBig);
  //textLeading(80);  // Set leading to 10
  text(line1, width/2, height/2);
}


void moduloSketch() {

  ellipseMode(TOP);

// top circle
  if (interval % 96 == 0)  {
    fill(0);
    ellipse(xPos,yPos,circleW,circleW);
    }

// 2nd circle
  if (interval % 48 == 0)  {
    fill(51);
    ellipse(xPos,yPos+(circleW*1),circleW,circleW);
    }

// 3rd circle
  if (interval % 24 == 0)  {
    fill(102);
    ellipse(xPos,yPos+(circleW*2),circleW,circleW);
    }

// 4th circle
  if (interval % 12 == 0)  {
    fill(153);
    ellipse(xPos,yPos+(circleW*3),circleW,circleW);
    }

// 5th circle
  if (interval % 6 == 0)  {
    fill(204);
    ellipse(xPos,yPos+(circleW*4),circleW,circleW);
    }


  interval = interval+ 1; // count each loop!
  // println("interval: "+interval);

  xPos++; // increment xPos
  // println("xPos: "+xPos);
  if (xPos >= width){ // if it gets to the edge, move down 1 row
    xPos = 0;
    yPos = yPos + (circleW * 5);
  }

  if (yPos >= height){ // if it gets to the bottom, start at the top again
    yPos = 0;
    background(255);
  }
} // end draw