turtles-own[pos vel isSolid?]

to setup
ca
let [:row screen-half-width]
let [:col -1 * screen-half-width]
let [:count 0]
repeat 1301 [
 crt 1
 ask-turtle :count [setxy :col :row]
 let [:count :count + 1]
 let [:col :col + 2]
 if :col > screen-half-width [ 
		let [:col :col - screen-width]
		let [:row :row - 1]
	]
]

ask-turtles [setc red setpos 0 setvel 0 setisSolid? false]
ask-turtles-with [ycor = 5 and xcor > -15 and xcor < 15] [setc brown setisSolid? true]
ask-turtles-with [ycor = 6 and xcor > -14 and xcor < 14] [setc brown setisSolid? true]
ask-turtles-with [ycor = 7 and xcor > -15 and xcor < 15] [setc brown setisSolid? true]
end

to go
  ask-turtle 650 [setpos -100 setvel 0]
  ask-turtle 650 [ setc yellow ]
end

to sense
 ask-turtles-with ((not (xcor = (-1 * screen-half-width))) and
		  (not (xcor = (screen-half-width))) and
		  (not (ycor = (screen-half-width))) and
		  (not (ycor = (-1 * screen-half-width))) and
		  (not (xcor = (-1 * screen-half-width + 1))) and
		  (not (xcor = (screen-half-width - 1))) and
		  (not (ycor = (screen-half-width - 1 ))) and
		  (not (ycor = (-1 * screen-half-width + 1))) )
 [
   go
 ]
end