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                <boton-x nombre-epico="Fili Santillán" url-epica=""></boton-x>

<boton-x nombre-epico="Nombre-1" url-epica=""></boton-x>

<boton-x nombre-epico="Nombre-2" url-epica=""></boton-x>



                boton-x {
  padding: 10px 20px;
  display: inline-block;
  background: #4299D4;
  border-radius: 5px;
  margin: 20px;
  box-shadow: 4px 4px 0 #1E252A;
  border: 1px solid #1E252A;

boton-x::shadow .link-x {
  color: #1E252A;
  text-decoration: none;
  font-family: 'Arial';
  font-size: 23px;
  letter-spacing: 4px;



                var miBoton = Object.create(HTMLElement.prototype);

miBoton.createdCallback = function() {

    var shadow = this.createShadowRoot(); // Creamos el Shadow Root
    var link = document.createElement("a"); // Creamos nuestro elemento "<a>"
    link.innerText = this.getAttribute("nombre-epico"); // Insertamos el valor que hay en "nombre-epico" como nodo en "<a>"
    link.href = this.getAttribute("url-epica"); // Agregamos el atributo href con el valor de "url-epica"
    link.className = "link-x"; // Agregamos la clase link-x
    shadow.appendChild(link); // Agregamos <a> al Shadow Root

var botonX = document.registerElement("boton-x", { 
    prototype: miBoton