Untitled

<html>
    <canvas id="gc" width="640" height="480"></canvas>
    <script>
        var ymover= 0;
        var score = 0;
        var enemyscore = 0;
        var velocityx = 1;
        var velocityy = 1;
        var ballx = 320;
        var speedy = 0;
        var speedx= -5;
        var center = ymover -50;
        var hitboxtop = ymover+ 50;
        var hitboxbottom = ymover- 50;
        var bally = 240
    window.onload= function() {
        c=document.getElementById('gc');
        cc=c.getContext('2d');
        document.addEventListener("keydown",keyPush)
        setInterval(update,1000/30);
    };
        function keyPush (evt) {
            switch(evt.keyCode) {
                case 83:
                    ymover += 10;
                    break;
                case 87:
                    ymover -= 10;
                    break;
            }
        }
    function update() {
        cc.fillStyle='black';
        cc.fillRect(0,0,c.width,c.height);
        cc.fillStyle='red';
        cc.fillRect(20,ymover,10,100);
        cc.fillStyle ='white';
        cc.fillText(score, 320, 240, 500);
        cc.fillRect(ballx, bally, 20, 20,);
        center = ymover-50;

        // Starting the paddle Code

        if (ymover>480) {
            ymover= 0;
        }
        else if (ymover<0) {
            ymover = 480;
        }
        else {
        }

        // Starting the Ball Code

        if (ballx >640) {
            score++;
            ballx = 320;
            speedy = 0;
            bally = 240;
            speedx = -speedx;
        }
        else if (ballx<0) {
            enemyscore++;
            ballx = 320;
            speedy = 0;
            bally = 240;
            speedx = -speedx;
        }
        if (ballx> 0 && ballx <40 && bally>hitboxbottom && bally<hitboxtop) {
            speedx = -speedx;
            console.log('collision');
            if (bally> hitboxbottom && bally< ymover) {
                speedy -= Math.floor(Math.random() * 5) + 2;
            }
            else if (bally<hitboxtop && bally> ymover) {
                speedy -= Math.floor(Math.random() * 5) + 2;
            }
        }
        if (bally>470) {
            bally = 469;
            speedy = -speedy;
        }
        else if (bally<10) {
            bally = 11;
            speedy = -speedy;
        }
        ballx += speedx*velocityx;
        bally += speedy;
        hitboxbottom = center-50;
        hitboxtop = center+50;
    }
    </script>
</html>