To achieve a flowing border effect, CSS animations can be used. In HTML, we need to create an element (eg div) and set it as a box with a certain width and height. We can then use CSS to define the element's border style, position, and animation.
First, we need to define our element in CSS. We can set the width, height and border style and width of this element. For example, in the following code, we set the width and height of the element to 200px, and set the border style to solid, border width to 4px, and border color to black:
.box {
width: 200px;
height: 200px;
border: 4px solid #000;
}
Next, we need to use CSS animations to achieve the flowing effect of the border. We can use the @keyframes rule to define keyframes for an animation, and then apply that animation to our element. In the code below, we define an animation called "border-flow" and apply it to our element:
.box {
animation: border-flow 2s linear infinite;
}
@keyframes border-flow {
0% {
border-left-color: #000;
border-top-color: #000;
}
25% {
border-top-color: transparent;
border-right-color: #000;
}
50% {
border-right-color: transparent;
border-bottom-color: #000;
}
75% {
border-bottom-color: transparent;
border-left-color: #000;
}
100% {
border-left-color: transparent;
border-top-color: #000;
}
}
In the code above, we define an animation called "border-flow" and apply it to our element. The animation has a duration of 2 seconds and is linear (i.e. proceeds at the same speed). We also set it to an infinite loop so the border will keep flowing.
In the @keyframes rule, we define the keyframes for the animation. We use the border-color property to define the color of the border. For example, in the first keyframe we set the left and top border colors to black ( border-left-color: #000; border-top-color: #000; ). In the second keyframe, we set the top border color to transparent and the right border color to black ( border-top-color: transparent; border-right-color: #000; ). We use a transparent border color to hide the border to create a flowing effect.
In the next two keyframes we set a different border color to black to create a flowing effect. Finally, in the last keyframe, we set the border color on the left to be transparent, and at the same time set the border color on the top to black, so that we complete a flow cycle of the border.
In short, it is very simple to use CSS animation to achieve border flow effect, just define a @keyframes rule and apply the animation to the element. By setting different border colors, we can create various flow effects.
Here is the full version of the code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.box {
width: 200px;
height: 200px;
border: 4px solid #000;
}
.box {
animation: border-flow 2s linear infinite;
}
@keyframes border-flow {
0% {
border-left-color: #000;
border-top-color: #000;
}
25% {
border-top-color: transparent;
border-right-color: #000;
}
50% {
border-right-color: transparent;
border-bottom-color: #000;
}
75% {
border-bottom-color: transparent;
border-left-color: #000;
}
100% {
border-left-color: transparent;
border-top-color: #000;
}
}
</style>
</head>
<body>
<div class="box"></div>
</body>
</html>