Reference source: Enable pygame event and set_timer(): https://www.itread01.com/content/1543591271.html python function: pass by reference https://stackoverflow.com/questions/13299427/python-functions-call-by-reference key table https://www.pygame.org/docs/ref/key.html#pygame.key.get_pressed remove "libpng warning: iCCP: known incorrect sRGB profile" https://stackoverflow.com/questions/22745076/libpng-warning-iccp-known-incorrect-srgb-profile/43415650