You can visualize a DirectedGraph as a 2-d graph that has a finite number of Nodes, with each Node located at some Point, and the adjacent Nodes joined (or connected) to each other by Edges.
Please pay attention to the subtle differences, particularly the Tangential line marking the fillet's point of contact with its adjacent surface, and how the reflections break there as well.
请注意细微的差别，尤其是切线标示出的倒圆角与临近面的连接处，还有在那里反射光是如何被打断的。
3
Look at all the reachable or walkable squares adjacent to the starting point, ignoring squares with walls, water, or other illegal terrain.