Challenge 2a: Reflection in the line y = a

Author:
NJT16
What stays the same and what changes as you move the points around? Are there any points that do not move under this transformation? Where would the co-ordinate (x,y) map to? 随着点的移动,什么保持不变,什么改变? 在此转换过程中,有没有要解决的问题? 坐标(x,y)会映射到哪里?
Created by N.Trubridge