How to override views->default->page->walled-garden.php

I'm starting with the custom_index and customize_style plugins.

I'm trying to style the log-in page.  The html is at  views->default->page->walled-garden.php

I want to make changes to the look of the login page which I think means creating a walled-garden.php somewhere in the customize_css tree or the custom_index tree.  I haven't figured this out yet.