import { LitElement } from 'lit';
export declare class Backdrop extends LitElement {
    open: boolean;
    invisible: boolean;
    transitionDuration: string;
    zIndex: number;
    static styles: import("lit").CSSResult;
    connectedCallback(): void;
    updated(changedProperties: Map<string, any>): void;
    private updateCSSVariables;
    private handleOpenChange;
    private handleEscapeKey;
    private handleClick;
    disconnectedCallback(): void;
    render(): import("lit-html").TemplateResult<1>;
}
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