Webleb - fragmentos de código - Juego de ping pong retro con JavaScript en HTML5 Canvas

<!DOCTYPE html>  
<html lang="en">  
<head>  
    <meta charset="UTF-8">  
    <title>Retro Ping Pong Game</title>  
    <meta name="viewport" content="width=device-width, initial-scale=1.0">  
      
    <style>  
        body {  
            background: #222;  
            color: #fff;  
            display: flex;  
            flex-direction: column;  
            align-items: center;  
            justify-content: flex-start;  
            min-height: 100vh;  
            font-family: 'Courier New', Courier, monospace;  
        }  
        h1 {  
            margin: 1rem 0 0.5rem 0;  
            letter-spacing: 2px;  
        }  
        #gameContainer {  
            display: flex;  
            flex-direction: column;  
            align-items: center;  
        }  
        canvas {  
            background: #000;  
            display: block;  
            margin: 0 auto;  
            border: 4px solid #fff;  
            border-radius: 8px;  
            box-shadow: 0 0 20px #fff7;  
        }  
        .instructions {  
            margin: 0.5rem 0 1rem 0;  
            font-size: 1.1rem;  
            color: #eee;  
        }  
    </style>  
</head>  
<body>  
      
    <h1>Retro Ping Pong</h1>  
    <div class="instructions">  
        Controls: <strong>W</strong> = Up, <strong>S</strong> = Down  
    </div>  
    <div id="gameContainer">  
          
        <canvas id="pong" width="640" height="400" aria-label="Ping Pong Game" tabindex="0"></canvas>  
    </div>  
      
    <script>  
        // --- Configuration ---  
        const canvas = document.getElementById('pong');  
        const context = canvas.getContext('2d');

// Paddle settings  
        const paddleWidth = 12, paddleHeight = 80;  
        const playerX = 10, cpuX = canvas.width - paddleWidth - 10;  
        let playerY = (canvas.height - paddleHeight) / 2;  
        let cpuY = (canvas.height - paddleHeight) / 2;  
        const paddleSpeed = 6;

// Ball settings  
        let ballX = canvas.width / 2, ballY = canvas.height / 2;  
        let ballRadius = 8;  
        let ballSpeedX = 5 * (Math.random() < 0.5 ? 1 : -1);  
        let ballSpeedY = 4 * (Math.random() < 0.5 ? 1 : -1);

// Scores  
        let playerScore = 0, cpuScore = 0;

// Controls  
        let upPressed = false, downPressed = false;

// --- Draw Functions ---  
        function drawRect(x, y, w, h, color) {  
            context.fillStyle = color;  
            context.fillRect(x, y, w, h);  
        }

function drawCircle(x, y, r, color) {  
            context.fillStyle = color;  
            context.beginPath();  
            context.arc(x, y, r, 0, Math.PI * 2, false);  
            context.closePath();  
            context.fill();  
        }

function drawText(text, x, y, color) {  
            context.fillStyle = color;  
            context.font = "32px Courier New, monospace";  
            context.fillText(text, x, y);  
        }

function drawNet() {  
            context.strokeStyle = "#fff";  
            context.setLineDash([8, 8]);  
            context.beginPath();  
            context.moveTo(canvas.width/2, 0);  
            context.lineTo(canvas.width/2, canvas.height);  
            context.stroke();  
            context.setLineDash([]);  
        }

// --- Main Draw ---  
        function draw() {  
            // Background  
            drawRect(0, 0, canvas.width, canvas.height, "#000");  
            drawNet();

// Player paddle (left)  
            drawRect(playerX, playerY, paddleWidth, paddleHeight, "#fff");  
            // CPU paddle (right)  
            drawRect(cpuX, cpuY, paddleWidth, paddleHeight, "#fff");

// Ball  
            drawCircle(ballX, ballY, ballRadius, "#fff");

// Scores  
            drawText(playerScore, canvas.width / 4, 40, "#fff");  
            drawText(cpuScore, canvas.width * 3 / 4, 40, "#fff");  
        }

// --- Game Update Logic ---  
        function update() {  
            // Player movement  
            if (upPressed && playerY > 0) playerY -= paddleSpeed;  
            if (downPressed && playerY < canvas.height - paddleHeight) playerY += paddleSpeed;

// CPU AI: tracks the ball  
            if (ballY < cpuY + paddleHeight / 2 && cpuY > 0) cpuY -= paddleSpeed * 0.85;  
            else if (ballY > cpuY + paddleHeight / 2 && cpuY < canvas.height - paddleHeight) cpuY += paddleSpeed * 0.85;

// Move ball  
            ballX += ballSpeedX;  
            ballY += ballSpeedY;

// Top and bottom wall collision  
            if (ballY - ballRadius < 0 || ballY + ballRadius > canvas.height) {  
                ballSpeedY *= -1;  
            }

// Left paddle collision (Player)  
            if (  
                ballX - ballRadius < playerX + paddleWidth &&  
                ballY > playerY &&  
                ballY < playerY + paddleHeight  
            ) {  
                ballX = playerX + paddleWidth + ballRadius; // prevent sticking  
                ballSpeedX *= -1.05; // bounce and speed up  
                // Add a bit of "spin" based on where it hits the paddle  
                let collidePoint = ballY - (playerY + paddleHeight/2);  
                ballSpeedY = collidePoint * 0.2;  
            }

// Right paddle collision (CPU)  
            if (  
                ballX + ballRadius > cpuX &&  
                ballY > cpuY &&  
                ballY < cpuY + paddleHeight  
            ) {  
                ballX = cpuX - ballRadius; // prevent sticking  
                ballSpeedX *= -1.05;  
                let collidePoint = ballY - (cpuY + paddleHeight/2);  
                ballSpeedY = collidePoint * 0.2;  
            }

// Left and Right wall (score)  
            if (ballX - ballRadius < 0) {  
                cpuScore += 1;  
                resetBall();  
            } else if (ballX + ballRadius > canvas.width) {  
                playerScore += 1;  
                resetBall();  
            }  
        }

// --- Reset Ball to Center ---  
        function resetBall() {  
            ballX = canvas.width / 2;  
            ballY = canvas.height / 2;  
            ballSpeedX = 5 * (Math.random() < 0.5 ? 1 : -1);  
            ballSpeedY = 4 * (Math.random() < 0.5 ? 1 : -1);  
        }

// --- Game Loop ---  
        function game() {  
            update();  
            draw();  
            requestAnimationFrame(game);  
        }

// --- Keyboard Input ---  
        document.addEventListener('keydown', function(e) {  
            if (e.key === 'w' || e.key === 'W' || e.key === 'ArrowUp') upPressed = true;  
            if (e.key === 's' || e.key === 'S' || e.key === 'ArrowDown') downPressed = true;  
        });  
        document.addEventListener('keyup', function(e) {  
            if (e.key === 'w' || e.key === 'W' || e.key === 'ArrowUp') upPressed = false;  
            if (e.key === 's' || e.key === 'S' || e.key === 'ArrowDown') downPressed = false;  
        });

// Accessibility: focus the canvas for keyboard input  
        canvas.focus();

// --- Start Game ---  
        game();  
    </script>  
</body>  
</html>

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