Interactive crosshairs in 15 LOC

crosshair.red

Red [Author: "Gregg Irwin"]

view [
	text bold "Crosshairs" text "Move the mouse"
	return
	base 640x480 water all-over
		draw [pen black  h-line: line 0x0 0x0  v-line: line 0x0 0x0]
		on-over [
		    h-line/2: as-pair 0 event/offset/y
		    h-line/3: as-pair 640 event/offset/y
	    	v-line/2: as-pair event/offset/x 0
	    	v-line/3: as-pair event/offset/x 480
		]
]