use constant PI => 3.14159265359;
# -----------------------------------------------------------
# Turtle Graph
my $h=0; my @x=(0); my @y=(0);
sub rt {$h = $h + shift;}
sub fd {
	$x[scalar @x] = $_[0]*sin(PI*$h/180) + $x[$#x]; 
	$y[scalar @y] = $_[0]*cos(PI*$h/180) + $y[$#y]; 
}
sub reset_xy {$h=0; @x=(0); @y=(0);}
# -----------------------------------------------------------


# -----------------------------------------------------------
# Koch Snowflake
sub koch {
	my ($d, $level) = @_ ;
	if ($level==0) {fd($d); return 1;} 
	rt(  0); koch($d/3,$level-1);
	rt(-60); koch($d/3,$level-1);
	rt(120); koch($d/3,$level-1);
	rt(-60); koch($d/3,$level-1);
}
# -----------------------------------------------------------
map {rt(120); koch(170, 4);} 0..2;
# -----------------------------------------------------------
plotxy([\@x,\@y], 'koch.jpg');
# -----------------------------------------------------------


# -----------------------------------------------------------
# Minkowski Island
sub minkowski {
	my ($d, $level) = @_ ;
	if ($level==0) {fd($d); return 1;} 
	minkowski($d/4,$level-1);
	rt(-90); minkowski($d/4,$level-1);
	rt( 90); minkowski($d/4,$level-1);
	rt( 90); minkowski($d/4,$level-1);
	minkowski($d/4,$level-1);
	rt(-90); minkowski($d/4,$level-1);
	rt(-90); minkowski($d/4,$level-1);
	rt( 90); minkowski($d/4,$level-1);
}
# -----------------------------------------------------------
reset_xy();	# if necessary
map {rt(90); minkowski(150, 3);} 0..3;
# -----------------------------------------------------------
plotxy([\@x,\@y], 'minkowski.jpg');
# -----------------------------------------------------------


# -----------------------------------------------------------
# Dragon Curve
sub dragon1 {
	my ($d, $level) = @_ ;
	if ($level==0) {fd($d); return 1;} 
	dragon($d*0.707,$level-1);
	rt(-90); dragon1($d*0.707,$level-1);
}
sub dragon {
	my ($d, $level) = @_ ;
	if ($level==0) {fd($d); return 1;} 
	dragon($d*0.707,$level-1);
	rt(90); dragon1($d*0.707,$level-1);
}
# -----------------------------------------------------------
reset_xy();	# if necessary
dragon(150, 12);
# -----------------------------------------------------------
plotxy([\@x,\@y], 'dragon.jpg');