The new variables in the Makefile, with defaults, are:
FIRE= XK_BackSpace:XK_Tab
FORWARD= XK_Up:XK_w
BACKWARD= XK_Down:XK_s
LEFT= XK_Left:XK_a
RIGHT= XK_Right:XK_d
WIDTH= 512
HEIGHT= 288
An example of how to set some is in the README.md file.
This commit means I can remove an item from the things-todo.md file
which I have now done. Next I can return to 2018.