¡Ya que va, que vuelva!

aquí mi ejercicio

<meta charset = "UTF8">
<h1>Programa V.4</h1>

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<canvas width = "600" height = "400"> </canvas>

<script>
    var pantalla = document.querySelector("canvas");
    var pincel = pantalla.getContext("2d");

    pincel.fillStyle = " #eaecee ";
    pincel.fillRect(0, 0, 600, 400);

    function designcircle(x,y,ratio){
    var posicion = Math.round(Math.random() * 10);
    var color = [" #cd6479 "," #cd64aa "," #b964cd "," #8764cd ","#6497cd"," #64cdc2 ","#6ecd64"," #f1f174 ","#ea6161"," #ffffff "," #000000 "]
    pincel.fillStyle = color[posicion];
    pincel.beginPath();
    pincel.arc(x,y,ratio,0,2*Math.PI);
    pincel.fill();
    }
    var x = 0;
    var sentido = 1
    function limpiar(){
        pincel.clearRect(0, 0, 600, 400);
    }
    function updatescreen() {
        limpiar();
        setInterval(designcircle(x,20,10),2500);
        if(x > 600){
            sentido = -1;
        }
        else if(x < 0){
            sentido = 1;
        }
        x = x + sentido;
        }

    setInterval(updatescreen,5);
</script>