> you have to explicitly specify mode: open The mode does not toggle the shadow DOM on and off. It just specifies whether or not the element's shadowRoot objec

> you have to explicitly specify mode: open The mode does not toggle the shadow DOM on and off. It just specifies whether or not the element's shadowRoot object is a public property. An open mode makes this possible: `document.querySelector('my-component').shadowRoot`. You have to explicitly opt-in to the shadow DOM either imperatively by calling `attachShadow`, or declaratively in HTML by giving the element a template child element with a `shadowrootmode` attribute.