You must complete the code so that it works as follows:

$1.$ The code in the initialize$()$ procedure of the Gosu window should be completed to set up cells that are connected to each other with variables joining each cell to its neighbours $($using references$).$

$2.$ The user should be able to left click on cells on the screen to create mazes $($and later in the Maze Search task we will use recursion to find a path through the maze$).$

$3.$ Each cell clicked on should turn yellow.

$4.$ Once this is working $($or perhaps before$)$ add code to print out each cell and indicate whether the reference to the neighbour on each side is nil or not, as per the following:

In this case there is no neighbour to the north or the west.

$($NB: whether the east or the west neighbour is nil will depend on your perspective $$ i$.$e is your perspective looking into the screen, or out of the screen$)$

Your submitted screenshot should look something like the following:

the code in question:

require 'gosu'

module ZOrder

BACKGROUND, MIDDLE, TOP $=*0.\mathrm{.}2$

end

MAP$\_$WIDTH $=200$

MAP$\_$HEIGHT $=200$

CELL$\_$DIM $=20$

class Cell

# have a pointer to the neighbouring cells

attr$\_$accessor :north, :south, :east, :west, :vacant, :visited, :on$\_$path

def initialize$()$

# Set all the pointers to nil

@north $=$ nil

@south $=$ nil

@east $=$ nil

@west $=$ nil

# record whether this cell is vacant

# default is not vacant i$.$e is a wall.

@vacant $=$ false

# this stops cycles $-$ set when you travel through a cell

@visited $=$ false

@on$\_$path $=$ false

end

end

# Instructions:

# Left click on cells to create a maze with at least one path moving from

# left to right. The right click on a cell for the program to find a path

# through the maze. When a path is found it will be displayed in red.

class GameWindow $$ Gosu::Window

# initialize creates a window with a width an a height

# and a caption. It also sets up any variables to be used.

# This is procedure i$.$e the return value is 'undefined'

def initialize

super MAP$\_$WIDTH, MAP$\_$HEIGHT, false

self.caption $=$ "Map Creation"

@path $=$ nil

x$\_$cell$\_$count $=$ MAP$\_$WIDTH $/$ CELL$\_$DIM

y$\_$cell$\_$count $=$ MAP$\_$HEIGHT $/$ CELL$\_$DIM

@columns $=$ Array.new$($x$\_$cell$\_$count$)$

column$\_$index $=0$

# first create cells for each position

while $($column$\_$index $$ x$\_$cell$\_$count$)$

row $=$ Array.new$($y$\_$cell$\_$count$)$

@columns$[$column$\_$index$]=$ row

row$\_$index $=0$

while $($row$\_$index $$ y$\_$cell$\_$count$)$

cell $=$ Cell.new$()$

@columns$[$column$\_$index$][$row$\_$index$]=$ cell

row$\_$index $+=1$

end

column$\_$index $+=1$

end

# now set up the neighbour links

# You need to do this using a while loop with another

# nested while loop inside.

end

# this is called by Gosu to see if should show the cursor $($or mouse$)$

def needs$\_$cursor?

true

end

# Returns an array of the cell x and y coordinates that were clicked on

def mouse$\_$over$\_$cell$($mouse$\_$x$,$ mouse$\_$y$)$

if mouse$\_$x CELL$\_$DIM

cell$\_$x $=0$

else

cell$\_$x $=($mouse$\_$x $/$ CELL$\_$DIM$).$to$\_$i

end

if mouse$\_$y CELL$\_$DIM

cell$\_$y $=0$

else

cell$\_$y $=($mouse$\_$y $/$ CELL$\_$DIM$).$to$\_$i

end

$[$cell$\_$x$,$ cell$\_$y$]$

end

# start a recursive search for paths from the selected cell

# it searches till it hits the East 'wall' then stops

# it does not necessarily find the shortest path

# Completing this function is NOT NECESSARY for the Maze Creation task

# complete the following for the Maze Search task $-$ after

# we cover Recusion in the lectures.

# But you DO need to complete it later for the Maze Search task

def search$($cell$\_$x $,$cell$\_$y$)$

dead$\_$end $=$ false

path$\_$found $=$ false

if $($cell$\_$x $==(($MAP$\_$WIDTH $/$ CELL$\_$DIM$)-1))$

if $($ARGV$.$length $>0)$ # debug

puts "End of one path x: $"+$ cell$\_$x$.$to$\_$s $+"$ y: $"+$ cell$\_$y$.$to$\_$s

end

$[[$cell$\_$x$,$cell$\_$y$]]$ # We are at the east wall $-$ exit

else

north$\_$path $=$ nil

west$\_$path $=$ nil

east$\_$path $=$ nil

south$\_$path $=$ nil

if $($ARGV$.$length $>0)$ # debug

puts "Searching. In cell x: $"+$ cell$\_$x$.$to$\_$s $+"$ y: $"+$ cell$\_$y$.$to$\_$s

end

# INSERT MISSING CODE HERE!! You need to have $4\text{'}$if$\text{'}$ tests to

# check each surrounding cell. Make use of the attributes for

# cells such as vacant, visited and on$\_$path.

# Cells on the outer boundaries will always have a nil on the

# boundary side

if $($column$\_$index $==0)$

cell.west $=$ nil

else

cell.west $=$ @columns$[$column$\_$index $-1][$row$\_$index$]$

end

if $($column$\_$index $==($x$\_$cell$\_$count $-1))$

cell.west $=$ nil

else

cell.west $=$ @columns$[$column$\_$index $-1][$row$\_$index$]$

end

# pick one of the possible paths that is not nil $($if any$)$:

if $($north$\_$path $!=$ nil$)$

path $=$ north$\_$path

elsif $($south$\_$path $!=$ nil$)$

path $=$ south$\_$path

elsif $($east$\_$path $!=$ nil$)$

path $=$ east$\_$path

elsif $($west$\_$path $!=$ nil$)$

path $=$ west$\_$path

end

# A path was found:

if $($path $!=$ nil$)$

if $($ARGV$.$length $>0)$ # debug

puts "Added x: $"+$ cell$\_$x$.$to$\_$s $+"$ y: $"+$ cell$\_$y$.$to$\_$s

end

$[[$cell$\_$x$,$cell$\_$y$]].$concat$($path$)$

else

if $($ARGV$.$length $>0)$ # debug

puts "Dead end x: $"+$ cell$\_$x$.$to$\_$s $+"$ y: $"+$ cell$\_$y$.$to$\_$s

end

nil # dead end

end

end

end

# Reacts to button press

# left button marks a cell vacant

# Right button