(1)-Changed mouse coordinate debug text. Now two coordinates are displayed: black is offset for play area, dark yellow is actual coordinate without offset. The actual coordinate will display outside of play area as well.  (2)-Added 'CPU Utilization' debug text. This relies on a third party called psutil.  The download URL is in the code comments, near the top of main.py. Game will still run without having psutil, but 'CPU Utilization' will show as '????'.  (3)-Added 'KILLALL' to 'Input' class. This kills/disappears all monsters in game. Useful for testing CPU load when 'max_monsters' is high and the 'MONSTER_SPAWN_EVENT' interval is small.
(1)-Fixed 'main menu' button within game; the problem was that the PygButton was being recreated every frame in '_draw_ui'.  (2)-Mouse cursor visibility is now handled within Input class via a new '_handle_mouse_visibility' method.  (3)-Game no longer starts in debug mode.  (4)-Capitalized on/off in OptionsPage; 'off' looked like 'orr' to me.  (5)-Some grammar and rewording of text within HelpPage.