Don't Display Read the Docs TOC on Narrow Windows

Read the Docs can use much less than half the window to display contents before the Table of Contents (sidebar ??) is turned off. How is the Table of Contents display disabled so the whole window width can be used to display content?

Varying content width with a stylesheet, conf.py reference and custom layout is explained in https://stackoverflow.com/a/33626140/4539999. I expect this framework would work with a stylesheet in source/_static with just the required css, e.g.

.wy-nav-content {
    max-width: 1200px !important;
}

I assume if screen width less than certain value set display_toc to false?