#! /usr/bin/perl -w


# Use bondage and discipline

use strict;
use POSIX qw( ceil );


# Set up vars

my $xmagnitude = 20;
my $ymagnitude = 20;
my @board;
my %dir = ("x" => 0,
           "y" => -1);
my $iterations = 1000;
my $pause = 1;

# Initialise board

for (my $y = 0; $y < $ymagnitude; ++$y)
{
        for (my $x = 0; $x < $xmagnitude; ++$x)
        {
                $board[$y][$x] = " ";
        }
}


# Find centre of board and X marks the spot

my %pos;
$pos{"x"} = ceil(($xmagnitude / 2) - 1);
$pos{"y"} = ceil(($ymagnitude / 2) - 1);
$board[$pos{"y"}][$pos{"x"}] = "X";


# start the loop

my $count = 0;
while ($count < $iterations)
{
        system(($^O eq 'MSWin32') ? 'cls' : 'clear'); # Thx QandA Editors
        map {print join ("", @$_)."\n"} @board;

        $pos{"x"} += $dir{"x"};
        $pos{"y"} += $dir{"y"};;

        # Exit if out of bounds

        if($pos{"x"} >= $ymagnitude || $pos{"x"} < 0 || $pos{"y"} >= $xmagnitude || $pos{"y"} < 0)
        {
                print "\nAnt has reached the edge of the board!\n\n";
                exit;
        }

        if ($board[$pos{"y"}][$pos{"x"}] eq "X")
        {
                # Turn left and make an O

                $board[$pos{"y"}][$pos{"x"}] = " ";

                # Remember your trig calculus

                my $tempvar = - $dir{"x"};
                $dir{"x"} = $dir{"y"};
                $dir{"y"} = $tempvar;

        }
        else
        {
                # Turn right and make an X

                $board[$pos{"y"}][$pos{"x"}] = "X";

                # Remember your trig calculus

                my $tempvar = - $dir{"y"};
                $dir{"y"} = $dir{"x"};
                $dir{"x"} = $tempvar;

        }

        ++$count;
        sleep $pause;

}

# ##### End of Script ##### #