The final value that motion can take is linear, which keeps animation speed constant.
最后，motion 属性还可以带的一个值是linear，该属性让动画以恒速变化。
youdao
This piecewise linear change has a very high practical value.
这种分段线性变化也有很高的实用价值。
应用推荐
模块上移
模块下移
不移动