Space Shooter Game - Kaizhelam

<canvas></canva>
<script type="text/javascript" charset="utf-8">
	window.onload = function() {
		var c = document.querySelector("canvas");
		var canvas = document.querySelector("canvas");
		c.width = innerWidth;
		c.height = innerHeight;
		c = c.getContext("2d");
		function startGame() {
			mouse = {
				x: innerWidth/2,
				y: innerHeight-33
			};
			touch = {
				x: innerWidth/2,
				y: innerHeight-33
			};
			canvas.addEventListener("mousemove", function(event) {
				mouse.x = event.clientX;
			});
			canvas.addEventListener("touchmove", function(event) {
				var rect = canvas.getBoundingClientRect();
				var root = document.documentElement;
				var touch = event.changedTouches[0];
				var touchX = parseInt(touch.clientX);
				var touchY = parseInt(touch.clientY) - rect.top - root.scrollTop;
				event.preventDefault();
				mouse.x = touchX;
				mouse.y = touchY;
			});
			var player_width = 32;
			var player_height = 32;
			var playerImg = new Image();
			var score = 0;
			var health = 100;
			playerImg.src = "https://image.ibb.co/dfbD1U/heroShip.png";
			var _bullets = [];
			var bullet_width = 6;
			var bullet_height = 8;
			var bullet_speed = 10;
			var _enemies = [];
			var enemyImg = new Image();
			enemyImg.src = "https://i.ibb.co/0YgHvmx/enemy-fotor-20230927153748.png"
			var enemy_width = 32;
			var enemy_height = 32;
			var _healthkits = [];
			var healthkitImg = new Image();
			healthkitImg.src = "https://image.ibb.co/gFvSEU/first_aid_kit.png";
			var healthkit_width = 32;
			var healthkit_height = 32;
			function Player(x, y, width, height) {
				this.x = x;
				this.y = y;
				this.width = width;
				this.height = height;
				this.draw = function() {
					c.beginPath();
					c.drawImage(playerImg, mouse.x-player_width, mouse.y-player_height);
				};
				this.update = function() {
					this.draw();
				};
			}
			function Bullet(x, y, width, height, speed) {
				this.x = x;
				this.y = y;
				this.width = width;
				this.height = height;
				this.speed = speed;
				this.draw = function() {
					c.beginPath();
					c.rect(this.x, this.y, this.width, this.height);
					c.fillStyle = "white";
					c.fill();
				};
				this.update = function() {
					this.y -= this.speed;
					this.draw();
				};
			}
			function Enemy(x, y, width, height, speed) {
				this.x = x;
				this.y = y;
				this.width = width;
				this.height = height;
				this.speed = speed;
				this.draw = function() {
					c.beginPath();
					c.drawImage(enemyImg, this.x, this.y);
				};
				this.update = function() {
					this.y += this.speed;
					this.draw();
				};
			}
			function Healthkit(x, y, width, height, speed) {
				this.x = x;
				this.y = y;
				this.width = width;
				this.height = height;
				this.speed = speed;
				this.draw = function() {
					c.beginPath();
					c.drawImage(healthkitImg, this.x, this.y);
				};
				this.update = function() {
					this.y += this.speed;
					this.draw();
				};
			}
			var __player = new Player(mouse.x, mouse.y, player_width, player_height);
			function drawEnemies() {
				for (var _ = 0; _ < 4; _++) {
					var x = Math.random()*(innerWidth-enemy_width);
					var y = -enemy_height;
					var width = enemy_width;
					var height = enemy_height;
					var speed = Math.random()*2;
					var __enemy = new Enemy(x, y, width, height, speed);
					_enemies.push(__enemy);
				}
			}setInterval(drawEnemies, 1234);
			function drawHealthkits() {
				for (var _ = 0; _ < 1; _++) {
					var x = Math.random()*(innerWidth-enemy_width);
					var y = -enemy_height;
					var width = healthkit_width;
					var height = healthkit_height;
					var speed = Math.random()*2.6;
					var __healthkit = new Healthkit(x, y, width, height, speed);
					_healthkits.push(__healthkit);
				}
			}setInterval(drawHealthkits, 15000);
			function fire() {
				for (var _ = 0; _ < 1; _++) {
					var x = mouse.x-bullet_width/2;
					var y = mouse.y-player_height;
					var __bullet = new Bullet(x, y, bullet_width, bullet_height, bullet_speed);
					_bullets.push(__bullet);
				}
			}setInterval(fire, 200);
			canvas.addEventListener("click", function() {});
			function collision(a, b) {
				return a.x < b.x + b.width &&
				a.x + a.width > b.x &&
				a.y < b.y + b.height &&
				a.y + a.height > b.y;
			}
			c.font = "1em Arial";
			function stoperror() {
				return true;
			}
			window.onerror = stoperror;
			function animate() {
				requestAnimationFrame(animate);
				c.beginPath();
				c.clearRect(0, 0, innerWidth, innerHeight);
				c.fillStyle = 'white';
				c.fillText("Health: " + health, 5, 20);
				c.fillText("Score: " + score, innerWidth-100, 20);
				__player.update();
				for (var i = 0; i < _bullets.length; i++) {
					_bullets[i].update();
					if (_bullets[i].y < 0) {
						_bullets.splice(i, 1);
					}
				}
				for (var k = 0; k < _enemies.length; k++) {
					_enemies[k].update();
					if (_enemies[k].y > innerHeight) {
						_enemies.splice(k, 1);
						health -= 10;
						if (health == 0) {
							alert("You DIED!\nYour score was "+score);
							startGame();
						}
					}
				}
				for (var j = _enemies.length-1; j >= 0; j--) {
					for (var l = _bullets.length-1; l >= 0; l--) {
						if (collision(_enemies[j], _bullets[l])) {
							_enemies.splice(j, 1);
							_bullets.splice(l, 1);
							score++;
						}
					}
				}
				for (var h = 0; h < _healthkits.length; h++) {
					_healthkits[h].update();
				}
				for (var hh = _healthkits.length-1; hh >= 0; hh--) {
					for (var hhh = _bullets.length-1; hhh >= 0; hhh--) {
						if (collision(_healthkits[hh], _bullets[hhh])) {
							_healthkits.splice(hh, 1);
							_bullets.splice(hhh, 1);
							health += 10;
						}
					}
				}
			}
			animate();
		}startGame();
	};
</script>
<style type="text/css" media="all">
	body {
		background: url('https://cdn.jsdelivr.net/gh/kaizhelam/Space-Shooter-Game@main/background.jpg');
		background-repeat: no-repeat;
		background-attachment: fixed;
		background-size: cover;
		display: flex;
		justify-content: center;
		align-items: center;
		height: 100vh;
		margin: 0;
	}
</style>

Hướng dẫn