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：
1 <style> 2 .balls { 3 border-radius: 50%; 4 position: fixed; 5 width: 50px; 6 height: 50px; 7 top: 60%; 8 animation-name: jump; 9 animation-duration: 2s; 10 animation-iteration-count: infinite; 11 } 12 #red { 13 background: red; 14 left: 25%; 15 animation-timing-function: linear; 16 } 17 #blue { 18 background: blue; 19 left: 50%; 20 animation-timing-function: cubic-bezier(0.311,0.441,0.444,1.649); 21 } 22 #green { 23 background: green; 24 left: 75%; 25 animation-timing-function: cubic-bezier(0.69, 0.1, 1, 0.1); 26 } 27 28 @keyframes jump { 29 50% { 30 top: 10%; 31 } 32 } 33 </style> 34 <div class="balls" id="red"></div> 35 <div class="balls" id="blue"></div> 36 <div class="balls" id="green"></div>
效果如下：
