Shield is a term used by Mecha to express theme in other CMS.
Info: This class is located in
Shield::$config = [ // List of alternative file extensions used by the shield files. // Shield files with `html` extension are a priority for the best performance. // To change the priority order, re-order this file extensions placement. 'x' = ['html', 'php'], // Set the name of the shield folder that you will use globally 'id' => 'document', // Change the first value to `body` to insert the generated // page classes to the `<body>` tag instead of `<html>` tag. // Second and third values of this configuration item are currently not used 'union' => ['html', "", ['class' => true]] ];