What is the usage of box-shadow in css3

In css3, the "box-shadow" attribute is used to add one or more shadows to the box and set the style of the shadow. The syntax is "box-shadow: horizontal shadow vertical shadow blur distance shadow size shadow Change the color of the outer shadow to the inner shadow;".

The operating environment of this tutorial: Windows 10 system, CSS3&&HTML5 version, Dell G3 computer.

What is the usage of box-shadow in css3

box-shadow: none | inset (optional value, not set, for outer projection, set, for inner projection) x-offset ( The horizontal offset of the shadow, the positive direction is right) y-offset (the vertical offset of the shadow, the positive direction is bottom) blur-radius (the blur radius of the shadow, which is positive, 0 means no blur effect, the larger the value, the blurr it is) spread-radius (shadow expansion radius, can be positive or negative) color (set the color of the object's shadow)

Attribute value description:

1.Shadow type: This parameter is optional, default The projection method is outer shadow; if the only value "inset" is taken, the outer shadow will be turned into an inner shadow

2. X-offset: refers to the horizontal offset of the shadow, and its value can be positive or negative. Positive value, the shadow is on the right side of the object, negative value, the shadow is on the left side of the object

3. Y-offset: refers to the vertical offset of the shadow, its value can also be positive or negative, positive value , the shadow is at the bottom of the object. When it is negative, the shadow is at the top of the object

4. Shadow blur radius: This parameter is optional and can only be positive. If its value is 0, it means that the shadow is not It has a blurring effect. The larger the value, the blurr the edge of the shadow.

5. Shadow expansion radius: This parameter is optional, and its value can be positive or negative. If it is positive, the entire shadow will be expanded. Otherwise, Then zoom out

6. Shadow color: This parameter is optional. When no color is set, the browser will use the default color, but the default color of each browser is different, especially in Safari and under the webkit kernel. The chrome browser will be colorless, that is, transparent. It is recommended not to omit this parameter.

**Note:** For multiple layers of shadows, the innermost layer has the highest priority, and then it decreases in sequence. Use commas "," to separate.

Practical application of box-shadow

Example 1: Do not set the X-axis and Y-axis, set the shadow blur radius to 15px, it will act within its own radius range and color.

box-shadow: 0 0 15px #f00;

Rendering:

Example 2: Set the X-axis and Y-axis to positive values ​​(positive values: X-axis to the right and Y-axis downward)

box-shadow:4px 4px 15px #f00;

Rendering:

box-shadow:0 0 15px #f00 inset;

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