int lineWeight;
color lineColor;
int drawMode;  // 0-eraser  1-brush 
float dx, dy, delta;
int pKey = -1;
int i;
float angle;
PFont font;

void setup(){

  size(400,200);
  background(255);

  lineWeight = 1;
  lineColor = color(random(255),random(255),random(255), random(40));
  drawMode = 1;
  font = loadFont("ArialNarrow-12.vlw");
  smooth();
}

void draw(){
  //get mouse speed
  dx = mouseX-pmouseX;
  dy = mouseY-pmouseY;
  delta = sqrt(dx*dx + dy*dy);
  if(mousePressed){
    // Use the mouse as a brush...
    if(drawMode == 1){
      stroke(lineColor);
      strokeWeight(lineWeight);
      for(i=0; i<200; i++){
        pushMatrix();
        translate(i,i);
        rotate(angle);
        bezier(mouseX*delta, pmouseY, 100, 10, 90, 200, pmouseX, mouseY*delta);
        bezier(400, 20, 10, 10, 90, 90, 15, 400);
        popMatrix();
      }
      angle += 0.2;
      for(int i = 0; i < 100; i++){
        pushMatrix();
        translate(i,i);
        rotate(delta);
        bezier(pmouseX+40, pmouseY-40, 20, 10, 20, 10,mouseX, mouseY);
        bezier(pmouseX-40, pmouseY+40, 20, 10, 20, 10,mouseY, mouseX);
        popMatrix();
      }
    } 

    // use the mouse as an eraser...
    else if(drawMode == 0){
      stroke(255);
      strokeWeight(delta);
      line(mouseX,mouseY,pmouseX,pmouseY);
      line(mouseY,mouseX,pmouseY,pmouseX); 
    }
  }  
}

void keyPressed(){
  // Erase Screen and create transparent background
  if(pKey != key){
    if(key == 't'){     
      background(0);
      fill(0,60);
      rect(0,0,width,height);
    } 
    // change line width
    else if(key == '1'){  
      lineWeight = 1; 
    }
    // increase line width
    else if(key == '2'){
      lineWeight = 2;
    } 

    // use the mouse as an eraser////
    else if(key == 'e'){
      drawMode = 0;
      lineColor = color(255);
    }
    //change line color
    else if(key == 'r'){
      drawMode = 1;
      lineColor = color(random(255),random(0),random(0), random(40));
    } 
    else if(key == 'g'){
      drawMode = 1;
      lineColor = color(random(0),random(255),random(0), random(40));
    } 
    else if(key == 'w'){
      drawMode = 1;
      lineColor = color(random(255),random(60));
    } 
    //USER GUIDE
      else if(key == '?'){
      textFont(font, 12); 
      fill(0);
      String s = "use r or g to change color - use e to erase - use t for transparent background - use 1/2 to change lineWidth - use ? to view the user guide";
      text(s, 15, 20, 200, 400);
    } 
  }
  pKey = key;
}
void keyReleased(){
  pKey = -1;
}