Sketchpad could do things like make lines perfectly parallel, the same length, straighten corners into perfect 90 degree intersections, and even scale shapes up and down dynamically.

Sketchpad 可以做一些事情，比如让线条完全平行、长度相同、将角拉直成完美的 90 度交叉点，甚至可以动态地上下缩放形状。