processing箭头动画

红色箭头向左跑出屏幕，且可以切换快速和慢速

PImage pic, button;
float posx=450, posy=220;
float speed=-1;
int col;
void setup() { 
  size(900, 600);
  pic = loadImage("pic1.png");
  button=loadImage("button.png");
}
void draw() {
  background(0);
  image(pic, -15, -20);
  rectgroud(posx, posy);
  rectgroud(posx-300, posy);
  rectgroud(posx+300, posy);
  posx +=speed;
  if (posx<-450) {
    posx=1250;
  }
  textSize(24);
  text("<<", 360, 556);
  text("<", 444, 556);
  stroke(155);
  strokeWeight(2);
  noFill();
  rect(340, 530, 80, 40);
  rect(420, 530, 80, 40);
  image(button, 525, 530, 40, 40);
}

void rectgroud(float x, float y) {
  fill(210, col, 0);
  noStroke();
  push();
  translate(x, y);
  rotate(PI/4);
  rect(0, -200, 100, 200);
  rect(0, 0, 300, 100);
  pop();
}

void mousePressed() {
  if (mouseX>340 &&  mouseX<420) {
    if (mouseY>530 && mouseY<570) {
      speed=-4;
    }
  } 
  if (mouseX>420 &&  mouseX<500) {
    if (mouseY>530 && mouseY<570) {
      speed=-2;
    }
  }
  if (dist(mouseX, mouseX, 545, 550)<20) {
    col=250;
  }
}
void mouseReleased() {
  speed=-1;
  col=0;
}