They are in the project that you can find in the "demos" folder of your local installation. The path matches the namespace, as with components by default. I am also attaching a short video that shows how you can see the relevant source code. If there is demo-specific CSS it is in inline <style> tags in the demo component. The Overview demo of the TileLayout does not have styles, and the shared styles used by the entire app are referenced from its wwwroot folder.
Regards,
Marin Bratanov
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