不透明度可以根据离摄像机的远近来确定，也就说，背景中的图形要更加不透明一些，给人以纵深感。

The opacity can depend on the distance to the camera, meaning that the images in the background can be a little transparent to give the feeling of depth.

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“header”和“content”查看器的背景颜色、圆角半径、边框和透明度都在外部css文件example . css的类选择器中定义(见清单19)。

The background color, corner radius, and border and thickness styles of "header" and "content" viewers are defined in class selectors of the external CSS file: "example.css" (Listing 19).

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我们对于这个上层的透明度设置为20%，这样的背景将是近黑色。

For this upper layer we set the transparency to 20% so the background will be nearly black.

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