Challenge 2a: Reflection in the line y = a

Author:
NJT16
Topic:
Reflection
What stays the same and what changes as you move the points around? Where would the co-ordinate (x,y) map to? 隨著點的移動，什麼保持不變，什麼改變？ 坐標（x，y）會映射到哪裡？
Created by N.Trubridge