void setup()
{
   background(0);
   strokeWeight(5);
}
void draw()
{
  stroke( 255 * int(key=='1') * int(mousePressed) + 
          200 * int(key=='2') * int(mousePressed) +
          150 * int(key=='3') * int(mousePressed) +
          100 * int(key=='4') * int(mousePressed));
        
  point(mouseX, mouseY);
  
}