gistfile1.pde

Train t;

void setup() {
  t = new Train();
  size(500, 500);
}

void draw() {
  background(255);
  t.update();
  t.display();
}

void keyPressed() {
  if (keyCode == UP) {
    t.speedUp();
  } else if (keyCode == DOWN) {
    t.slowDown();
  } else if (keyCode == RIGHT) {
    t.turn("right");
  } else if (keyCode == LEFT) {
    t.turn("left");
  }
}
void keyReleased() {
  t.coast();
}

class Train {
  PVector loc;
  PVector vel;
  PVector acc;
  float angle;
  Train() {
    loc = new PVector(250, 250);
    vel = new PVector(0, 0);
    acc = new PVector(0, 0);
    angle = 0;
  }
  void update() {
    vel.add(acc);
    loc.add(vel);
  }
  void speedUp() {
    acc = new PVector(0, -0.1);
  }
  void slowDown() {
    acc = new PVector(0, 0.1);
  }
  void turn(String dir) {
    if (dir == "left") {
      angle = angle - 0.1;
    } else if (dir == "right") {
      angle = angle + 0.1;
    }
  }
  void coast() {
    acc.mult(0);
  }
  void display() {
    pushMatrix();
    translate(loc.x, loc.y);
    rotate(angle);
    rectMode(CENTER);
    rect(0, 0, 20, 40);
    popMatrix();
  }
}