Pure CSS3 creates an animated special effect where the border shadow spreads outwards-CSS Tutorial-php.cn

Pure CSS3 creates an animated special effect where the border shadow spreads outwards

青灯夜游

Release： 2021-08-30 09:50:39

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In the previous article "Teach you step-by-step how to use CSS3 to implement dynamic effects of button hovering and flashing", we introduced the use of CSS3 to add dynamic effects to buttons and achieve a button hovering and flashing shadow animation effect. If you are interested, you can learn about it~

Today, this article will share with you a border animation effect. Let’s see how to use CSS3 to achieve the animation effect of the border shadow spreading outward.

Let’s take a look at the renderings first:

Pure CSS3 creates an animated special effect where the border shadow spreads outwards

Let’s study how to achieve this effect:

First create the HTML part , define a div container, containing the text:

<div id="box">
	编程是为那些有不同想法的人准备的。。。<br /> 
	对于那些想要创造伟大事物并愿意改变世界的人。
</div>

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Pure CSS3 creates an animated special effect where the border shadow spreads outwards

and then start defining css styles for modification : Adjust layout style, background color, div center alignment, font color

body {
	display: flex;
	align-items: center;
	justify-content: center;
	height: 100vh;
	background: #00ac69;
}
#box {
	font-family: Arial;
	font-size: 18px;
	line-height: 30px;
	font-weight: bold;
	color: white;
	border: 2px solid;
	padding: 15px;
}

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Pure CSS3 creates an animated special effect where the border shadow spreads outwards

Right angles don’t look good, we can use border-radius to align the four corners of the border Set to rounded corners

#box {
	border-radius: 10px;
}

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Pure CSS3 creates an animated special effect where the border shadow spreads outwards

##The following is the most critical, creating the animation effect of the shadow spreading outward:We use animation and @keyframes to achieve

First bind animation to the #box element, use the animation attribute to specify a name for the @keyframes animation, set the time it takes to complete the animation, and the speed curve of the animation.

#box {
	animation: animated-border 1.5s infinite;
}

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Then use @keyframes to set the action of each frame of the animation
Here is the beginning of setting the animation (0%{} ), the border-shadow is
box-shadow: 0 0 0 0 rgba(255, 255, 255, 0.4);; then when the animation is completed (100%{}), the border-shadow is box-shadow: 0 0 0 20px rgba(255, 255, 255, 0);, the shadow distance becomes larger and the color becomes transparent.

@keyframes animated-border {
	0% {
		box-shadow: 0 0 0 0 rgba(255, 255, 255, 0.4);
	}

	100% {
		box-shadow: 0 0 0 20px rgba(255, 255, 255, 0);
	}
}

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Pure CSS3 creates an animated special effect where the border shadow spreads outwards

OK, you’re done! The complete code is attached below:

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<style type="text/css">
			body {
				display: flex;
				align-items: center;
				justify-content: center;
				height: 100vh;
				background: #00ac69;
			}

			#box {
				font-family: Arial;
				font-size: 18px;
				line-height: 30px;
				font-weight: bold;
				color: white;
				border: 2px solid;
				padding: 15px;
				border-radius: 10px;
				animation: animated-border 1.5s infinite;
			}

			@keyframes animated-border {
				0% {
					box-shadow: 0 0 0 0 rgba(255, 255, 255, 0.4);
				}

				100% {
					box-shadow: 0 0 0 20px rgba(255, 255, 255, 0);
				}
			}
		</style>
	</head>
	<body>
		<div id="box">
			编程是为那些有不同想法的人准备的。。。<br />
			对于那些想要创造伟大事物并愿意改变世界的人。
		</div>
	</body>
</html>

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Finally, I will introduce to you the key attributes

animation and @keyframes:

animation Property is a shorthand property that can set multiple animation properties in a single declaration:

animation-name：指定要绑定到选择器的关键帧的名称
animation-duration：动画指定需要多少秒或毫秒完成
animation-timing-function：设置动画将如何完成一个周期
animation-delay：设置动画在启动前的延迟间隔。
animation-iteration-count：定义动画的播放次数。
animation-direction：指定是否应该轮流反向播放动画。
animation-fill-mode：规定当动画不播放时（当动画完成时，或当动画有一个延迟未开始播放时），要应用到元素的样式。
animation-play-state：指定动画是否正在运行或已暂停。

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@keyframes Rules are used to define CSS animations A periodic behavior; needs to be used together with the animation attribute to create simple animation effects.

@keyframe rules consist of the keyword "@keyframe", followed by an identifier giving the name of the animation (which will be referenced using animation-name), followed by a set of style rules (separated by braces). The animation is then applied to the element by using the identifier as the value of the animation-name attribute. For example:

/* 定义动画*/
@keyframes 动画名称{
    /* 样式规则*/
}
/* 将它应用于元素 */
.element {
    animation-name: 动画名称（在@keyframes中已经声明好的）;
    /* 或使用动画简写属性*/
    animation: 动画名称 1s ...
}

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Inside the braces of the @keyframes rule, we need to define keyframes or waypoints that specify the value of the property being animated at a specific point during the animation. This allows us to control intermediate steps in the animation sequence. For example, in the above example:

@keyframes animated-border {
	0% {
		box-shadow: 0 0 0 0 rgba(255, 255, 255, 0.4);
	}

	100% {
		box-shadow: 0 0 0 20px rgba(255, 255, 255, 0);
	}
}

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