appendix gturtlescreen methods method description screen register_shape(nameshape=noneadds turtle shape to turtlescreen' shapelist arguments( name is the name of gif-file and shape is none installs the corresponding image shape !image-shapes do not rotate when turning the turtle!so they do not display the heading of the turtle( name is an arbitrary string and shape is tuple of pairs of coordinates installs the corresponding polygon shape ( name is an arbitrary string and shape is (compoundshape object installs the corresponding compound shape to use shapeyou have to issue the command shape(shapenamecallregister_shape("turtle gif"-orregister_shape("tri"(( , )( , )(- , ))example (for turtlescreen instance named screen)screen register_shape("triangle"(( ,- ),( , ),(- ,- ))screen reset(reset all turtles on the screen to their initial state example (for turtlescreen instance named screen)screen reset(screen screensize(canvwidth=nonecanvheight=nonebg=noneresize the canvas the turtles are drawing on optional argumentscanvwidth positive integernew width of canvas in pixels canvheight positive integernew height of canvas in pixels bg colorstring or color-tupelnew backgroundcolor if no arguments are givenreturn current (canvaswidthcanvasheightdo not alter the drawing window to observe hidden parts of the canvas use the scrollbars (can make visible those parts of drawingwhich were outside the canvas before!example (for turtle instance named turtle)turtle screensize( , ## to search for an erroneously escaped turtle ;-this copy belongs to 'acha