FXML :
<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.layout.AnchorPane?>


<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" stylesheets="@../../css/light.css" xmlns="http://javafx.com/javafx/21" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <AnchorPane layoutX="161.0" layoutY="85.0" prefHeight="181.0" prefWidth="297.0" styleClass="test-pane" />
   </children>
</AnchorPane>

CSS:
.base{
    -fx-background-color: #0D1116;
}
.test-pane{
    -fx-background-color: #0D1116;
    -fx-border-color: #1A1D23;
    -fx-effect: dropshadow(gaussian, rgba(0, 0, 0, 0.75), 10, 0.5, 0, 2);
}