# installExplorerTheme **Kind:** Function **Source:** [`atloria-monorepo/packages/ui-core/src/components/api-explorer/theme.ts`](https://github.com/sherkety/atloria/blob/main/atloria-monorepo/packages/ui-core/src/components/api-explorer/theme.ts#L232) Put the mode-resolving sheet in the host document, once. It has to live in the light DOM: only there can a selector see `` and read the mode off it. Everything the sheet sets is a custom property on the explorer's own elements, so nothing outside the explorer changes — and from those elements the values inherit down through every shadow root the explorer opens. Called from `connectedCallback`, which runs before the first render, so the very first paint is already themed. ## Signature ```ts function installExplorerTheme(doc: Document): void ``` ## Parameters | Name | Type | |---|---| | `doc` | `Document` | **Returns:** `void`