Vê se assim resolve... P.S.: Dessa forma ele anda na diagonal Document #canvas{ · sandroSaraujo

Vê se assim resolve...
P.S.: Dessa forma ele anda na diagonal
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        #canvas{
            height: 400;
            width: 400;
            background-color: aquamarine;
        }
        .flex {
          -webkit-flex: 1;
          flex: 1;
        }
    </style>

</head>
<body>

    <canvas id="canvas"></canvas>
    <div class="flex">
       <pre id="console-log"></pre>
    </div>

    <script>
        var gameReady = true;
        let consoleLog = document.getElementById('console-log')
        const canvas = document.getElementById('canvas')
        const ctx = canvas.getContext('2d')
        var x = canvas.width/2    //começa no meio do x (player)
        var y = canvas.height/2   //começa no meio do y (player)
        var vel = 1
		
        function messageLog(message) {
           consoleLog.innerHTML += `${message}<br>`;
        }
		
        var Keys = {
           up: false,
           down: false,
           left: false,
           right: false
        };

        //objeto player com propriedades do quadrado
        var player = {
            color: 'black',
            altura: '10',
            largura: '10',
            position: {
                coordx: x,
                coordy: y
            }
        }

        //desestruturação do objeto player
        var {color, altura, largura, position, mover} = player

        //le a tecla digitada
        window.onkeydown = function(e){
            //messageLog(`Key "${event.key}" pressed [event: keypress]`);
             var kc = e.keyCode;
             e.preventDefault();

             if(kc === 37) Keys.left = true;
             if(kc === 38) Keys.up = true;
             if(kc === 39) Keys.right = true;
             if(kc === 40) Keys.down = true;
        } 
		
        window.onkeyup = function(e){
             var kc = e.keyCode;
             e.preventDefault();

             if(kc === 37) Keys.left = false;
             if(kc === 38) Keys.up = false;
             if(kc === 39) Keys.right = false;
             if(kc === 40) Keys.down = false;
        }
		
        function move() {

            if(Keys.up) {
				player.position.coordy -= vel;
            }

            if(Keys.down) {
                player.position.coordy += vel;
            }

            if(Keys.left) {
                player.position.coordx -= vel;
            }

            if(Keys.right) {
                player.position.coordx += vel;
            }
        }

        //desenha o player na tela
        function draw() {
                move()
                ctx.clearRect(0, 0, canvas.width, canvas.height)
                ctx.fillRect(position.coordx, position.coordy, largura, altura)
                ctx.fillStyle = color
                requestAnimationFrame(draw) //looping do programa
        }
          //inicio do programa
        draw();

    </script>
</body>
</html>