Do not cross the center line.

请不要穿越中线。

I keep one foot near the center line.

我经常保持一个脚靠近中场。

Symmetry for the center line of the sieve.

与筛体中心线对称。

Repeat this on the other side of center line.

重复对中线的另一边的。

Which center line is bigger? Actually, they're exactly the same size.

哪个中心圆大写？实际上，他们是完全相同的大小。