Line is simply a point that moves continuously, like the edge of a shape or the motion of a single brush stroke.
线就是点的连续移动，比如图形的边，或者画笔笔触的移动轨迹。
2
Add a little extra touch to the stroke by drawing a 1px line with the Pencil Tool vertically up the entire edge.
在整个边线上再用铅笔工具画1px的垂线。
3
The edge of the wharf and buildings need to be better defined, so I applied a "stroke" to the colored layers. This is where having the layers separated out worked to my advantage.