let fire;

​

let shipPositionX;

let shipPositionY;

let shipDirectionX;

let shipDirectionY;

let shipAngle;

let shipSpeed;

let shipRadius;

let shipMaxSpeed;

let shipAcceleration;

let shipFriction;

let shipScore;

let shipLife;

​

let gunPositionX;

let gunPositionY;

let gunRadius;

​

let bulletPositionX = [];

let bulletPositionY = [];

let bulletDirectionX = [];

let bulletDirectionY = [];

let bulletSpeed = [];

let bulletRadius = [];

let bulletStatus = [];

let maxBullets;

​

let asteroidPositionX = [];

let asteroidPositionY = [];

let asteroidDirectionX = [];

let asteroidDirectionY = [];

let asteroidRadius = [];

let asteroidSpeed = [];

let asteroidStatus = [];

let maxAsteroid;

​

function setup() {

  ratioX = 9; ratioY = 6;  viewportScale = 70;

  createCanvas(ratioX * viewportScale, ratioY * viewportScale);

  fire = 0;

  //Ship Initialization

  shipPositionX = (ratioX * viewportScale)/2;

  shipPositionY = (ratioY * viewportScale)/2;

  shipDirectionX = cos(0.5);

  shipDirectionY = sin(0.8);

  shipAngle = 0;

  shipSpeed = 0;

  shipRadius = 20;

  shipMaxSpeed = 5.5;//try 50 Teerathep

  shipAcceleration = 0.05;  

  shipFriction = 0.030;

  shipScore = 0;

  shipLife = 5;

  //Gun Initialization

  gunPositionX = shipPositionX;

  gunPositionY = shipPositionY;

  gunRadius = shipRadius + 1.2;

  maxBullets = 200;

  for(i=0;i<maxBullets;i++)

  {

    bulletPositionX[i] = gunPositionX;

    bulletPositionY[i] = gunPositionY;

    bulletDirectionX[i] = shipDirectionX;

    bulletDirectionY[i] = shipDirectionY;

    bulletSpeed[i] = 7;

    bulletRadius[i] = 4;

    bulletStatus[i] = false; //0 == off

  }

  maxAsteroid = 15;

  for(i=0;i<maxAsteroid;i++)

  {  

    asteroidPositionX[i] = random(0, ratioX * viewportScale);

    asteroidPositionY[i] = random(0, ratioY * viewportScale);

    asteroidDirectionX[i] = random(-1,1);

    asteroidDirectionY[i] = random(-1,1);

    asteroidRadius[i] = random(5,45);

    asteroidSpeed[i] = random(2, 5);

    asteroidStatus[i] = true;

  }    

}

​

function draw() {

  background(0);

  if(shipLife)

    {

  playerInput();

  updateShipDirection();

  updateShipPosition();

  updateGunPosition();

  if(bulletStatus)

   updateBulletPosition();//Later on we are going to have many bullets

  updateAsteroid();

    }

  drawGameObjects();

​

}

​

function playerInput()

{

 if(keyIsDown(38))//UP_ARROW is a constant with value 38

   {

     shipSpeed = shipSpeed + shipAcceleration;

     if(shipSpeed >shipMaxSpeed)

        shipSpeed = shipMaxSpeed;

   }

 if(keyIsDown(LEFT_ARROW))

   {

     shipAngle = shipAngle - 0.02; //Its in radian

   }

  else if(keyIsDown(RIGHT_ARROW))

   {

     shipAngle = shipAngle + 0.02; //Its in radian

   }

  if(fire)

   {fire=0;

     //Search for an status false bullet

     for(i=0; i<maxBullets;i++)

       if(bulletStatus[i] == false)

         break;

     bulletStatus[i] = true;

     bulletPositionX[i] = gunPositionX + shipDirectionX*gunRadius;

     bulletPositionY[i] = gunPositionY + shipDirectionY*gunRadius;

     bulletDirectionX[i] = shipDirectionX * bulletSpeed[i];

     bulletDirectionY[i] = shipDirectionY * bulletSpeed[i];

     //print(bulletDirectionX[i],bulletDirectionY[i]);

   }

}

​

function updateShipDirection()

{

  shipDirectionX = cos(shipAngle);

  shipDirectionY = sin(shipAngle);

}

​

function updateShipPosition()// P = P + Vt  or P = P + direction * speed 

{

  if(shipSpeed < 0)

    shipSpeed = 0;

  else

    shipSpeed = shipSpeed - shipFriction;

  shipPositionX = shipPositionX + shipDirectionX * shipSpeed;

  shipPositionY = shipPositionY + shipDirectionY * shipSpeed;

  if(shipPositionX < 0)

      shipPositionX = ratioX * viewportScale;

  else if(shipPositionX > ratioX * viewportScale)

      shipPositionX = 0;

  else if(shipPositionY < 0)

      shipPositionY = ratioY * viewportScale;

  else if(shipPositionY > ratioY * viewportScale)

      shipPositionY = 0;

  //Check for Asteriod

  for(i=0; i<maxAsteroid ;i++)//For every Asteroid

    if(asteroidStatus[i])

     {

        if(pointCircleIntersection(shipPositionX,shipPositionY, asteroidPositionX[i],asteroidPositionY[i], asteroidRadius[i]))

          {

             asteroidStatus[i] = false;

             shipLife = shipLife - 1; 

          }

      }

}

​

function updateGunPosition()

{ 

  gunPositionX = shipPositionX;

  gunPositionY = shipPositionY;

}

​

function updateBulletPosition()

{

  for(i=0;i<maxBullets;i++)

       if(bulletStatus[i] == true)

         {

            bulletPositionX[i] = bulletPositionX[i] + bulletDirectionX[i];

            bulletPositionY[i] = bulletPositionY[i] + bulletDirectionY[i];

         }

  for(i=0;i<maxBullets;i++)

    if(outOfBound(bulletPositionX[i], bulletPositionY[i]))

      bulletStatus[i] = false;

}

function updateAsteroid()

{ 

  //Check for bullet intersection

  for(i=0; i<maxAsteroid ;i++)//For every Asteroid

    if(asteroidStatus[i])

    for(j=0; j<maxBullets; j++)////Check all the bullet distances

      {

        if(bulletStatus[j] && pointCircleIntersection(bulletPositionX[j],bulletPositionY[j], asteroidPositionX[i],asteroidPositionY[i], asteroidRadius[i]))

          {

             asteroidStatus[i] = false;

             bulletStatus[j] = false;

             shipScore = shipScore + 1000; 

          }

      }

  for(i=0;i<maxAsteroid;i++)//Update position

      if(asteroidStatus[i] == true)

      {

          asteroidPositionX[i] = asteroidPositionX[i] + asteroidDirectionX[i];

          asteroidPositionY[i] = asteroidPositionY[i] + asteroidDirectionY[i];           }  

  for(i=0;i<maxAsteroid;i++)//Wrap the Asteroid

    if(outOfBound(asteroidPositionX[i], asteroidPositionY[i]))

      {

        if(asteroidPositionX[i] < 0)

          asteroidPositionX[i] = ratioX * viewportScale;

        else if(asteroidPositionX[i] > ratioX * viewportScale)

          asteroidPositionX[i] = 0;

        else if(asteroidPositionY[i] < 0)

          asteroidPositionY[i] = ratioY * viewportScale;

        else if(asteroidPositionY[i] > ratioY * viewportScale)

          asteroidPositionY[i] = 0;

      }

}

​

function drawGameObjects()

{

  //Drawing the ship

  stroke(255,255,255);

  strokeWeight(shipRadius);

  point(shipPositionX, shipPositionY);

  //Drawing the gun

  strokeWeight(2);

  line(gunPositionX, gunPositionY, 

       gunPositionX + (shipDirectionX*gunRadius),

    gunPositionY + (shipDirectionY*gunRadius));

  //Drawing the bullet(s)

  strokeWeight(5);

  for(i=0;i<maxBullets;i++)

   if(bulletStatus[i])

     point(bulletPositionX[i],bulletPositionY[i]);

  //Drawing the Asteroids

  strokeWeight(1);fill(180);

  for(i=0;i<maxAsteroid;i++)

   if(asteroidStatus[i])

     circle(asteroidPositionX[i],asteroidPositionY[i], asteroidRadius[i]);

  strokeWeight(1);fill(255);

  text(shipScore, 50,20); 

  //text(shipLife, 50, 35);

  for(i=0;i<shipLife;i++)

    text("O", 50+(i*15), 35);

  if(shipLife == 0)

    text("Game Over", ratioX * viewportScale/2-20, ratioY * viewportScale/2);

}

​

function outOfBound(x, y)

{

  if(x < 0 || x > ratioX * viewportScale || y <0 || y > ratioY * viewportScale)

    return true;

  else

    return false;

}

​

function keyPressed() {

  if (keyCode === 32) 

  {

    fire = 1;

  } else 

    fire = 0;

}

​

function pointCircleIntersection(pointX, pointY, circleCenterX, circleCenterY, circleRadius)

{

  let diffX = circleCenterX - pointX;

  let diffY = circleCenterY - pointY;

  let squaredDistance = diffX*diffX + diffY*diffY;

  if(squaredDistance > circleRadius*circleRadius)

    return false;

  return true;

}

​