let y = 250;

​

let vx = 25;

let vy = 0;

​

let deltaVx = 0;

let deltaVy = 0;

​

let theta;

​

let Fthrust = 30;

let mass = 3;

let dt = 0.1;

​

let r = 12;

​

let thrusting = false;

let reversing = false;

​

let xhistory = [];

let yhistory = [];

​

let iterations = 0;

​

function setup() {

  createCanvas(750, 500);

  theta = HALF_PI;

}

​

function draw() {

  background(255);

​

  vx += deltaVx;

  vy += deltaVy;

​

  x += vx * dt;

  y += vy * dt;

​

  deltaVx = 0;

  deltaVy = 0;

​

  if (keyIsDown(LEFT_ARROW)) {

    theta += 0.1;

  }

​

  if (keyIsDown(RIGHT_ARROW)) {

    theta -= 0.1;

  }

​

  if (keyIsDown(UP_ARROW)) {

    let accelx = Fthrust * cos(theta) / mass;

    deltaVx = accelx * dt;

    let accely = Fthrust * sin(theta) / mass;

    deltaVy = accely * dt;

    thrusting = true;

  } else {

    thrusting = false;

  }

​

  if (keyIsDown(DOWN_ARROW)) {

    let accelx = -Fthrust * cos(theta) / mass;

    deltaVx = accelx * dt;

    let accely = -Fthrust * sin(theta) / mass;

    deltaVy = accely * dt;

    reversing = true;

  } else {

    reversing = false;

  }

​

  let buffer = r * 2;

​

  if (x > width + buffer) {

    x = -buffer;

  } else if (x < -buffer) {

    x = width + buffer;

  }

  if (y > height + buffer) {

    y = -buffer;

  } else if (y < -buffer) {

    y = height + buffer;

  }

​

  strokeWeight(2);

  noFill();

  stroke(0);

  push();

  translate(x, height - y);

  rotate(HALF_PI - theta);

  fill(175);

  beginShape();

  vertex(-r, r);

  vertex(0, -1.5 * r);

  vertex(r, r);

  endShape(CLOSE);

  if (thrusting || reversing) {

    push();

    if (thrusting) {

      fill(255, 165, 0);

    }

    if (reversing) {

      fill(0, 0, 255);

    }

    noStroke();

    rect(-r / 2, r + 1, r, 15);

    pop();

  }

  pop();

​

  if (iterations % 5 == 1) {

    xhistory.push(x);

    yhistory.push(y);

  }

​

  iterations++;

​

  let maxLength = 50;

  if (xhistory.length > maxLength) {

    xhistory = xhistory.slice(xhistory.length - maxLength);

    yhistory = yhistory.slice(yhistory.length - maxLength);

  }

  for (i = 0; i < xhistory.length; i++) {

    strokeWeight(3);

    point(xhistory[i], height - yhistory[i]);

  }

}