@vaadin/vaadin-lumo-styles/src/mixins/menu-overlay-core.css

Lumo is a design system foundation for modern web applications, used by Vaadin components

/**
 * @license
 * Copyright (c) 2017 - 2026 Vaadin Ltd.
 * This program is available under Apache License Version 2.0, available at https://vaadin.com/license/
 */
@media lumo_mixins_menu-overlay-core {
  :host([opening]),
  :host([closing]) {
    animation: 0.14s lumo-overlay-dummy-animation;
  }

  [part='overlay'] {
    will-change: opacity, transform;
  }

  :host([opening]) [part='overlay'] {
    animation: 0.1s lumo-menu-overlay-enter ease-out both;
  }

  @keyframes lumo-menu-overlay-enter {
    0% {
      opacity: 0;
      transform: translateY(-4px);
    }
  }

  :host([closing]) [part='overlay'] {
    animation: 0.1s lumo-menu-overlay-exit both;
  }

  @keyframes lumo-menu-overlay-exit {
    100% {
      opacity: 0;
    }
  }
}