This challenge animates an element to replicate the movement of a ball being juggled. Prior challenges covered the linear and ease-out cubic Bezier curves, however neither depicts the juggling movement accurately. You need to customize a Bezier curve for this.
The animation-timing-function automatically loops at every keyframe when the animation-iteration-count is set to infinite. Since there is a keyframe rule set in the middle of the animation duration (at 50%), it results in two identical animation progressions at the upward and downward movement of the ball.
The following cubic Bezier curve simulates a juggling movement:
cubic-bezier(0.3, 0.4, 0.5, 1.6);
Notice that the value of y2 is larger than 1. Although the cubic Bezier curve is mapped on an 1 by 1 coordinate system, and it can only accept x values from 0 to 1, the y value can be set to numbers larger than one. This results in a bouncing movement that is ideal for simulating the juggling ball.
练习题目:
Change value of the animation-timing-function of the element with the id of green to a cubic-bezier function with x1, y1, x2, y2 values set respectively to 0.311, 0.441, 0.444, 1.649.
练习代码：
<style>
.balls {
border-radius: 50%;
position: fixed;
width: 50px;
height: 50px;
top: 60%;
animation-name: jump;
animation-duration: 2s;
animation-iteration-count: infinite;
}
#red {
background: red;
left: 25%;
animation-timing-function: linear;
}
#blue {
background: blue;
left: 50%;
animation-timing-function: cubic-bezier(0.311,0.441,0.444,1.649);
}
#green {
background: green;
left: 75%;
animation-timing-function: cubic-bezier(0.69, 0.1, 1, 0.1);
} @keyframes jump {
50% {
top: 10%;
}
}
</style>
<div class="balls" id="red"></div>
<div class="balls" id="blue"></div>
<div class="balls" id="green"></div>
效果如下：
