<canvas id="ctx" width="500" height="500" style="border:1px solid #000000;"></canvas>

<script>
var ctx = document.getElementById("ctx").getContext("2d");
ctx.font = '30px Arial';

var HEIGHT = 500;
var WIDTH = 500;
var timeWhenGameStarted = Date.now();	//return time in ms

var frameCount = 0;

var score = 0;
var player;

Entity = function(type,id,x,y,spdX,spdY,width,height,color){
	var self = {
		type:type,
		x:x,
		spdX:spdX,
		y:y,
		spdY:spdY,
		width:width,
		height:height,
		color:color,
	};
	self.update = function(){
		self.updatePosition();
		self.draw();
	}
	self.updatePosition = function(){
		if(self.type === 'player'){
			if(self.pressingRight)
				self.x += 10;
			if(self.pressingLeft)
				self.x -= 10;
			if(self.pressingDown)
				self.y += 10;
			if(self.pressingUp)
				self.y -= 10;

			//ispositionvalid
			if(self.x < self.width/2)
				self.x = self.width/2;
			if(self.x > WIDTH-self.width/2)
				self.x = WIDTH - self.width/2;
			if(self.y < self.height/2)
				self.y = self.height/2;
			if(self.y > HEIGHT - self.height/2)
				self.y = HEIGHT - self.height/2;

		} else {
			self.x += self.spdX;
			self.y += self.spdY;

			if(self.x < 0 || self.x > WIDTH){
				self.spdX = -self.spdX;
			}
			if(self.y < 0 || self.y > HEIGHT){
				self.spdY = -self.spdY;
			}
		}
	}
	self.getDistance = function (entity2){	//return distance (number)
		var vx = self.x - entity2.x;
		var vy = self.y - entity2.y;
		return Math.sqrt(vx*vx+vy*vy);
	}
	self.testCollision = function(entity2){	//return if colliding (true/false)
		var rect1 = {
			x:self.x-self.width/2,
			y:self.y-self.height/2,
			width:self.width,
			height:self.height,
		}
		var rect2 = {
			x:entity2.x-entity2.width/2,
			y:entity2.y-entity2.height/2,
			width:entity2.width,
			height:entity2.height,
		}
		return testCollisionRectRect(rect1,rect2);
	}
	self.draw = function(){
		ctx.save();
		ctx.fillStyle = self.color;
		ctx.fillRect(self.x-self.width/2,self.y-self.height/2,self.width,self.height);
		ctx.restore();
	}

	return self;
}

Actor = function(type,id,x,y,spdX,spdY,width,height,color){
	var self = Entity(type,id,x,y,spdX,spdY,width,height,color);

	self.attackCounter = 0;
	self.aimAngle = 0;
	self.atkSpd = 1;

	self.performAttack = function(){
		if(self.attackCounter > 25){	//every 1 sec
			self.attackCounter = 0;
			generateBullet(self);
		}
	}
	self.performSpecialAttack = function(){
		if(self.attackCounter > 50){	//every 1 sec
			self.attackCounter = 0;
			/*
			for(var i = 0 ; i < 360; i++){
				generateBullet(self,i);
			}
			*/
			generateBullet(self,self.aimAngle - 5);
			generateBullet(self,self.aimAngle);
			generateBullet(self,self.aimAngle + 5);
		}
	}
	return self;
}

Player = function(){
	var p = Actor('player','myId',50,40,30,5,20,20,'green');

	p.pressingDown = false;
	p.pressingUp = false;
	p.pressingLeft = false;
	p.pressingRight = false;
	return p;
}

var enemyList = {};
var upgradeList = {};
var bulletList = {};

Enemy = function(id,x,y,spdX,spdY,width,height){
	var self = Actor('enemy',id,x,y,spdX,spdY,width,height,'red');
	enemyList[id] = self;
}

randomlyGenerateEnemy = function(){
	//Math.random() returns a number between 0 and 1
	var x = Math.random()*WIDTH;
	var y = Math.random()*HEIGHT;
	var height = 10 + Math.random()*30;	//between 10 and 40
	var width = 10 + Math.random()*30;
	var id = Math.random();
	var spdX = 5 + Math.random() * 5;
	var spdY = 5 + Math.random() * 5;
	Enemy(id,x,y,spdX,spdY,width,height);

}

Upgrade = function(id,x,y,spdX,spdY,width,height,color,category){
	var self = Entity('upgrade',id,x,y,spdX,spdY,width,height,color);
	self.category = category;
	upgradeList[id] = self;
}

randomlyGenerateUpgrade = function(){
	//Math.random() returns a number between 0 and 1
	var x = Math.random()*WIDTH;
	var y = Math.random()*HEIGHT;
	var height = 10;
	var width = 10;
	var id = Math.random();
	var spdX = 0;
	var spdY = 0;

	if(Math.random()<0.5){
		var category = 'score';
		var color = 'orange';
	} else {
		var category = 'atkSpd';
		var color = 'purple';
	}

	Upgrade(id,x,y,spdX,spdY,width,height,color,category);
}

Bullet = function (id,x,y,spdX,spdY,width,height){
	var self = Entity('bullet',id,x,y,spdX,spdY,width,height,'black');
	self.timer = 0;
	bulletList[id] = self;
}

generateBullet = function(actor,aimOverwrite){
	//Math.random() returns a number between 0 and 1
	var x = actor.x;
	var y = actor.y;
	var height = 10;
	var width = 10;
	var id = Math.random();

	var angle;
	if(aimOverwrite !== undefined)
		angle = aimOverwrite;
	else angle = actor.aimAngle;

	var spdX = Math.cos(angle/180*Math.PI)*5;
	var spdY = Math.sin(angle/180*Math.PI)*5;
	Bullet(id,x,y,spdX,spdY,width,height);
}

testCollisionRectRect = function(rect1,rect2){
	return rect1.x <= rect2.x+rect2.width
		&& rect2.x <= rect1.x+rect1.width
		&& rect1.y <= rect2.y + rect2.height
		&& rect2.y <= rect1.y + rect1.height;
}

document.onclick = function(mouse){
	player.performAttack();
}

document.oncontextmenu = function(mouse){
	player.performSpecialAttack();
	mouse.preventDefault();
}

document.onmousemove = function(mouse){
	var mouseX = mouse.clientX - document.getElementById('ctx').getBoundingClientRect().left;
	var mouseY = mouse.clientY - document.getElementById('ctx').getBoundingClientRect().top;

	mouseX -= player.x;
	mouseY -= player.y;

	player.aimAngle = Math.atan2(mouseY,mouseX) / Math.PI * 180;
}

document.onkeydown = function(event){
	if(event.keyCode === 68)	//d
		player.pressingRight = true;
	else if(event.keyCode === 83)	//s
		player.pressingDown = true;
	else if(event.keyCode === 65) //a
		player.pressingLeft = true;
	else if(event.keyCode === 87) // w
		player.pressingUp = true;
}

document.onkeyup = function(event){
	if(event.keyCode === 68)	//d
		player.pressingRight = false;
	else if(event.keyCode === 83)	//s
		player.pressingDown = false;
	else if(event.keyCode === 65) //a
		player.pressingLeft = false;
	else if(event.keyCode === 87) // w
		player.pressingUp = false;
}

update = function(){
	ctx.clearRect(0,0,WIDTH,HEIGHT);
	frameCount++;
	score++;

	if(frameCount % 100 === 0)	//every 4 sec
		randomlyGenerateEnemy();

	if(frameCount % 75 === 0)	//every 3 sec
		randomlyGenerateUpgrade();

	player.attackCounter += player.atkSpd;


	for(var key in bulletList){
		bulletList[key].update();

		var toRemove = false;
		bulletList[key].timer++;
		if(bulletList[key].timer > 75){
			toRemove = true;
		}

		for(var key2 in enemyList){
			var isColliding = bulletList[key].testCollision(enemyList[key2]);
			if(isColliding){
				toRemove = true;
				delete enemyList[key2];
				break;
			}
		}
		if(toRemove){
			delete bulletList[key];
		}
	}

	for(var key in upgradeList){
		upgradeList[key].update();
		var isColliding = player.testCollision(upgradeList[key]);
		if(isColliding){
			if(upgradeList[key].category === 'score')
				score += 1000;
			if(upgradeList[key].category === 'atkSpd')
				player.atkSpd += 3;
			delete upgradeList[key];
		}
	}

	for(var key in enemyList){
		enemyList[key].update();

		var isColliding = player.testCollision(enemyList[key]);
		if(isColliding){
			player.hp = player.hp - 1;
		}
	}
	if(player.hp <= 0){
		var timeSurvived = Date.now() - timeWhenGameStarted;
		console.log("You lost! You survived for " + timeSurvived + " ms.");
		startNewGame();
	}
	player.update();
	ctx.fillText(player.hp + " Hp",0,30);
	ctx.fillText('Score: ' + score,200,30);
}

startNewGame = function(){
	player.hp = 10;
	timeWhenGameStarted = Date.now();
	frameCount = 0;
	score = 0;
	enemyList = {};
	upgradeList = {};
	bulletList = {};
	randomlyGenerateEnemy();
	randomlyGenerateEnemy();
	randomlyGenerateEnemy();

}

player = Player();
startNewGame();

setInterval(update,40);












</script>