So you want to add a .h file
•Add it to every .o/.cpp that #includes it, directly or indirectly.
runmaze.o : runmaze.cpp Maze.h SquareMaze.h MazeRunner.h RandomMazeRunner.h VisualizeSquareMazeRunner.h Fictitious.h
g++ -Wall -c -g runmaze.cpp
MazeRunner.o : MazeRunner.cpp Maze.h MazeRunner.h Fictitious.h
g++ -Wall -c -g MazeRunner.cpp
RandomMazeRunner.o : RandomMazeRunner.cpp Maze.h MazeRunner.h RandomMazeRunner.h
g++ -Wall -c -g RandomMazeRunner.cpp
But RandomMazeRunner.cpp doesn’t #include Fictitious.h
(in our example)