GUI handles things related to the user interface. Stuff like font rendering and size of the user interface.

List of variables:

Variable name	Variable type	Description	Default(beta 4.22)
clickTimeTolerance	positive decimal value	how long time in seconds before a click is no longer a click	0.3
clcikTolerance	positive decimal value	how far in pixels the mouse may move before a click is not longer a click	3.5
crispFontFactor	positive decimal value	amount of crispiness on the fonts.. Don't touch, default is good enough	0.5
crispFonts	true or false	Whether or not to use crisp fonts	false
font	string	what font to use. Only fixedsys and arial_black are supported as of now	"arial_black"
fontShadow	true or false	whether or not to render shadows of text	true
fontShadowOffset	array of two decimal values	XY offset of shadow	[0.0625, 0.0625]
forceOSCursor	true or false	force operating system cursor or use the phun cursors	false
opaqueness	positive decimal value	transparency of user interface	0.9
scale	positive decimal value	scale of user interface	1.0