color couleurHaut = #FF00FF;
color couleurBas = #FFFF3F;
int multiple = 1;
boolean txt = true;

void setup()
{
  size(300,400); 
}

void draw()
{
  background (couleurHaut);
  for (int i=0; i<height; i++)
  {
    stroke (couleurBas, (255*(height-i)/multiple*height));
    line (0, i, width, i);
  }
  if (txt)
  {
    PFont font;
    font = loadFont("SynchroLET-48.vlw"); 
    textFont(font, 20);
    textAlign(CENTER);
    String s = "Each click change image";
    text(s, width/3, (width/2), 80, 80);
    s = "Made by BE-Art";
    text(s, 0, height-40, 100, 100);
    s = "under Creative Commons licence";
    text(s, 200, height-75,100,100);
  }
}

void mousePressed()
{
  multiple=int(random(0,49)+1);
  txt = false;
}