pong/gunfight.html

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<!DOCTYPE html>
<html>
<head>
<title></title>
<style>
html, body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
</style>
</head>
<body>
<canvas width="565" height="500" id="game"></canvas>
<script>
const canvas = document.getElementById('game');
const context = canvas.getContext('2d');
const grid = 15;
const playerHeight = grid * 3; // 45
const maxPlayerY = canvas.height - grid - playerHeight;
var playerSpeed = 4;
const leftPlayer = {
// start in the middle of the game on the left side
x: grid * 2,
y: canvas.height / 2 - playerHeight / 2,
width: grid,
height: playerHeight,
// shooting cooldown
cooldown: 0,
// player velocity
dy: 0
};
const rightPlayer = {
// start in the middle of the game on the right side
x: canvas.width - grid * 3,
y: canvas.height / 2 - playerHeight / 2,
width: grid,
height: playerHeight,
// shooting cooldown
cooldown: 0,
// player velocity
dy: 0
};
const bullets = {
speed: 5,
array: []
}
// check for collision between two objects using axis-aligned bounding box (AABB)
// @see https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection
function collides(obj1, obj2) {
return obj1.x < obj2.x + obj2.width &&
obj1.x + obj1.width > obj2.x &&
obj1.y < obj2.y + obj2.height &&
obj1.y + obj1.height > obj2.y;
}
// game loop
function loop() {
requestAnimationFrame(loop);
context.clearRect(0,0,canvas.width,canvas.height);
// bullet cooldowns
// left player
if (leftPlayer.cooldown > 0) {
leftPlayer.cooldown--;
}
// right player
if (rightPlayer.cooldown > 0) {
rightPlayer.cooldown--;
}
// move players by their velocity
leftPlayer.y += leftPlayer.dy;
rightPlayer.y += rightPlayer.dy;
// prevent players from going through walls
if (leftPlayer.y < grid) {
leftPlayer.y = grid;
}
else if (leftPlayer.y > maxPlayerY) {
leftPlayer.y = maxPlayerY;
}
if (rightPlayer.y < grid) {
rightPlayer.y = grid;
}
else if (rightPlayer.y > maxPlayerY) {
rightPlayer.y = maxPlayerY;
}
// draw bullets
context.fillStyle = 'yellow';
bullets.array.forEach(function(bullet, index) {
context.fillRect(bullet.x, bullet.y, 10, 5);
// check if the bullet hits a player
// left player
if (collides(bullet, leftPlayer)) {
bullets.array.splice(index, 1);
leftPlayer.y = canvas.height / 2 - playerHeight / 2;
rightPlayer.y = canvas.height / 2 - playerHeight / 2;
bullets.array.length = 0;
}
// right player
else if (collides(bullet, rightPlayer)) {
bullets.array.splice(index, 1);
leftPlayer.y = canvas.height / 2 - playerHeight / 2;
rightPlayer.y = canvas.height / 2 - playerHeight / 2;
bullets.array.length = 0;
}
// move bullets
bullet.x += bullet.dx;
// remove bullets that leave the screen
if (bullet.x < 0 || bullet.x > canvas.width) {
bullets.array.splice(index, 1);
}
});
// draw paddles
context.fillStyle = 'gold';
context.fillRect(leftPlayer.x, leftPlayer.y, leftPlayer.width, leftPlayer.height);
context.fillRect(rightPlayer.x, rightPlayer.y, rightPlayer.width, rightPlayer.height);
// draw walls
context.fillStyle = 'lightgray';
context.fillRect(0, 0, canvas.width, grid);
context.fillRect(0, canvas.height - grid, canvas.width, canvas.height);
}
// listen to keyboard events to move the players
document.addEventListener('keydown', function(e) {
// up arrow key
if (e.which === 38) {
rightPlayer.dy = -playerSpeed;
}
// down arrow key
else if (e.which === 40) {
rightPlayer.dy = playerSpeed;
}
// w key
if (e.which === 87) {
leftPlayer.dy = -playerSpeed;
}
// a key
else if (e.which === 83) {
leftPlayer.dy = playerSpeed;
}
// shooting
// left arrow key
if (e.which === 37 && rightPlayer.cooldown === 0) {
bullets.array.push({
x: rightPlayer.x - 10,
y: rightPlayer.y + 20,
width: 10,
height: 5,
dx: -bullets.speed
});
rightPlayer.cooldown = 25;
}
// d key
if (e.which === 68 && leftPlayer.cooldown === 0) {
bullets.array.push({
x: leftPlayer.x + 15,
y: leftPlayer.y + 20,
width: 10,
height: 5,
dx: bullets.speed
});
leftPlayer.cooldown = 25;
}
});
// listen to keyboard events to stop the player if key is released
document.addEventListener('keyup', function(e) {
if (e.which === 38 || e.which === 40) {
rightPlayer.dy = 0;
}
if (e.which === 83 || e.which === 87) {
leftPlayer.dy = 0;
}
});
// start the game
requestAnimationFrame(loop);
</script>
</body>
</html>