The readme and documentation is in the source. Please read that.
The config maps the right-hand keys to screen grid cells, four on each screen:
UI OP
JK L;
By mashing (Ctrl-Alt-Cmd) the buttons, focus is switched to the window in the relevant cell, mashing the same button multiple times cycles focus between windows in the cell.
If you hard-mash (Shift-Ctrl-Alt-Cmd) these buttons, the focused window is moved to cover the relevant cell, doing it twice makes it expand across the screen vertically.