So how can I choose and apply between two different sets of CSS rules, based on the width available to the form, instead of the viewport width itself?

那么如何在两组不同的CSS规则之间进行选择和应用，基于窗体的宽度，而不是视口宽度本身？

youdao

As shown in Figure 2, Figure 3, Figure 4, and Figure 5, changes in font size and viewport width can have potentially dramatic effects on visual elements placed on the page.

如图2、图3、图4和图5所示，字体大小和浏览器窗口宽度的改变会对页面上的可视元素产生显著影响。

youdao

The viewport settings I chose for this application set the width of the page to the width of the device's current orientation.

我为该应用程序所选的视窗设置将把页面的宽度设为设备当前方位的宽度。

youdao

All of a sudden, it seemed that there was a conceptually easy way to make a single website look good on multiple screen sizes just worry about the pixel width of the viewport.

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The whole practice of responsive web design that has evolved over the past two years as the most expedient way to deal with getting web content to look decent on the ever-proliferating variety of mobile devices is based on the width of the viewport.

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