diff --git a/README.markdown b/README.markdown
index 1c147f542..e8e296949 100644
--- a/README.markdown
+++ b/README.markdown
@@ -73,7 +73,7 @@ The author is Alessandro Ranellucci (me).
         --help              Output this usage screen and exit
         
       Printer options:
-        --nozzle-diameter   Diameter of nozzle in mm (default: 0.45)
+        --nozzle-diameter   Diameter of nozzle in mm (default: 0.55)
         --print-center      Coordinates of the point to center the print around 
                             (default: 100,100)
         --use-relative-e-distances
@@ -90,9 +90,11 @@ The author is Alessandro Ranellucci (me).
       Speed options:
         --print-feed-rate   Speed of print moves in mm/sec (default: 60)
         --travel-feed-rate  Speed of non-print moves in mm/sec (default: 130)
+        --perimeter-feed-rate
+                            Speed of print moves for perimeters in mm/sec (default: 60)
         --bottom-layer-speed-ratio
                             Factor to increase/decrease speeds on bottom 
-                            layer by (default: 0.6)
+                            layer by (default: 0.3)
         
       Accuracy options:
         --layer-height      Layer height in mm (default: 0.4)
@@ -104,15 +106,18 @@ The author is Alessandro Ranellucci (me).
                             (range: 1+, default: 3)
         --fill-density      Infill density (range: 0-1, default: 0.4)
         --fill-angle        Infill angle in degrees (range: 0-90, default: 0)
-        --temperature       Extrusion temperature (default: 195)
+        --temperature       Extrusion temperature (default: 200)
       
       Retraction options:
         --retract-length    Length of retraction in mm when pausing extrusion 
-                            (default: 2)
+                            (default: 1)
         --retract-speed     Speed for retraction in mm/sec (default: 40)
         --retract-restart-extra
                             Additional amount of filament in mm to push after
                             compensating retraction (default: 0)
+        --retract-before-travel
+                            Only retract before travel moves of this length (default: 1)
+       
        Skirt options:
         --skirts            Number of skirts to draw (default: 1)
         --skirt-distance    Distance in mm between innermost skirt and object 
@@ -125,3 +130,4 @@ The author is Alessandro Ranellucci (me).
         --multiply-x        Number of items along X axis (1+, default: 1)
         --multiply-y        Number of items along Y axis (1+, default: 1)
         --multiply-distance Distance in mm between copies (default: 6)
+        
diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index a8fbbdb03..6098f95ea 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -26,7 +26,7 @@ use Slic3r::Surface;
 use Slic3r::Surface::Collection;
 
 # printer options
-our $nozzle_diameter    = 0.5;
+our $nozzle_diameter    = 0.55;
 our $print_center       = [100,100];  # object will be centered around this point
 our $use_relative_e_distances = 0;
 our $z_offset = 0;
@@ -38,6 +38,7 @@ our $filament_packing_density = 0.85;
 # speed options
 our $print_feed_rate            = 60;   # mm/sec
 our $travel_feed_rate           = 130;   # mm/sec
+our $perimeter_feed_rate        = 30;   # mm/sec
 our $bottom_layer_speed_ratio   = 0.3;
 
 # accuracy options
@@ -57,6 +58,7 @@ our $temperature        = 200;
 our $retract_length         = 1;    # mm
 our $retract_restart_extra  = 0;    # mm
 our $retract_speed          = 40;   # mm/sec
+our $retract_before_travel  = 1;    # mm
 
 # skirt options
 our $skirts             = 1;
diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index ce7015d8b..04f4d50a7 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -6,7 +6,7 @@ has 'shift_y'            => (is => 'ro', default => sub {0} );
 has 'z'                  => (is => 'rw', default => sub {0} );
 
 has 'extrusion_distance' => (is => 'rw', default => sub {0} );
-has 'retracted'          => (is => 'rw', default => sub {0} );
+has 'retracted'          => (is => 'rw', default => sub {1} );  # this spits out some plastic at start
 has 'last_pos'           => (is => 'rw', default => sub { [0,0] } );
 
 # calculate speeds
@@ -18,6 +18,10 @@ has 'print_feed_rate' => (
     is      => 'ro',
     default => sub { $Slic3r::print_feed_rate * 60 },  # mm/min
 );
+has 'perimeter_feed_rate' => (
+    is      => 'ro',
+    default => sub { $Slic3r::perimeter_feed_rate * 60 },  # mm/min
+);
 has 'retract_speed' => (
     is      => 'ro',
     default => sub { $Slic3r::retract_speed * 60 },  # mm/min
@@ -39,8 +43,12 @@ sub move_z {
     my $self = shift;
     my ($z) = @_;
     
-    # TODO: retraction
-    return $self->G1(undef, $z, 0, 'move to next layer');
+    my $gcode = "";
+    
+    $gcode .= $self->retract;
+    $gcode .= $self->G1(undef, $z, 0, 'move to next layer');
+    
+    return $gcode;
 }
 
 sub extrude_loop {
@@ -72,15 +80,17 @@ sub extrude {
         $gcode .= "G92 E0 ; reset extrusion distance\n";
     }
     
+    # retract
+    if (Slic3r::Geometry::distance_between_points($self->last_pos, $path->points->[0]->p) 
+        >= $Slic3r::retract_before_travel) {
+        $gcode .= $self->retract;
+    }
+    
     # go to first point of extrusion path
     $gcode .= $self->G1($path->points->[0], undef, 0, "move to first $description point");
     
     # compensate retraction
-    if ($self->retracted) {
-        $gcode .= $self->G1(undef, undef, ($Slic3r::retract_length + $Slic3r::retract_restart_extra), 
-            "compensate retraction");
-        $self->retracted(0);
-    }
+    $gcode .= $self->unretract if $self->retracted;
     
     # extrude while going to next points
     foreach my $line ($path->lines) {
@@ -94,15 +104,26 @@ sub extrude {
         $gcode .= $self->G1($line->b, undef, $e, $description);
     }
     
-    # retract
-    if ($Slic3r::retract_length > 0) {
-        $gcode .= $self->G1(undef, undef, -$Slic3r::retract_length, "retract");
-        $self->retracted(1);
-    }
-    
     return $gcode;
 }
 
+sub retract {
+    my $self = shift;
+    return "" unless $Slic3r::retract_length > 0 
+        && $self->extrusion_distance > 0 
+        && !$self->retracted;
+    
+    $self->retracted(1);
+    return $self->G1(undef, undef, -$Slic3r::retract_length, "retract");
+}
+
+sub unretract {
+    my $self = shift;
+    $self->retracted(0);
+    return $self->G1(undef, undef, ($Slic3r::retract_length + $Slic3r::retract_restart_extra), 
+        "compensate retraction");
+}
+
 sub G1 {
     my $self = shift;
     my ($point, $z, $e, $comment) = @_;
@@ -116,7 +137,7 @@ sub G1 {
             ($point->y * $Slic3r::resolution) + $self->shift_y; #**
         $self->last_pos($point->p);
     }
-    if ($z && $z != $self->z) {
+    if (defined $z && $z != $self->z) {
         $self->z($z);
         $gcode .= sprintf " Z%.${dec}f", $z;
     }
@@ -129,11 +150,12 @@ sub G1 {
     if ($e) {
         $self->extrusion_distance(0) if $Slic3r::use_relative_e_distances;
         $self->extrusion_distance($self->extrusion_distance + $e);
-        $gcode .= sprintf " F%.${dec}f E%.5f", 
-            $e < 0 
-                ? $self->retract_speed
-                : ($self->print_feed_rate * $speed_multiplier), 
-            $self->extrusion_distance;
+        my $speed = $self->print_feed_rate * $speed_multiplier;
+        $speed = $self->retract_speed if $comment =~ /retract/;
+        $speed = $self->perimeter_feed_rate * $speed_multiplier if $comment =~ /perimeter/;
+        
+        $gcode .= sprintf " F%.${dec}f E%.5f", $speed, $self->extrusion_distance;
+        
     } else {
         $gcode .= sprintf " F%.${dec}f", ($self->travel_feed_rate * $speed_multiplier);
     }
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index b97a214fc..51e556d98 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -26,6 +26,32 @@ has 'layers' => (
     default => sub { [] },
 );
 
+sub new_from_stl {
+    my $self = shift;
+    my ($stl_file) = @_;
+    
+    my $print = Slic3r::STL->new->parse_file($stl_file);
+    
+    print "\n==> PROCESSING SLICES:\n";
+    foreach my $layer (@{ $print->layers }) {
+        printf "\nProcessing layer %d:\n", $layer->id;
+    
+        # build polylines of lines which do not already belong to a surface
+        my $polylines = $layer->make_polylines;
+        
+        # build surfaces of polylines (distinguishing contours from holes)
+        $layer->make_surfaces($polylines);
+        
+        # merge surfaces having a common line
+        $layer->merge_contiguous_surfaces;
+    }
+    
+    # detect which surfaces are near external layers
+    $print->discover_horizontal_shells;
+    
+    return $print;
+}
+
 sub layer_count {
     my $self = shift;
     return scalar @{ $self->layers };
diff --git a/lib/Slic3r/STL.pm b/lib/Slic3r/STL.pm
index 6565389c2..2f9492f22 100644
--- a/lib/Slic3r/STL.pm
+++ b/lib/Slic3r/STL.pm
@@ -89,23 +89,6 @@ sub parse_file {
             $self->_facet($print, $normal, @copy_vertices);
         }
     }
-    
-    print "\n==> PROCESSING SLICES:\n";
-    foreach my $layer (@{ $print->layers }) {
-        printf "\nProcessing layer %d:\n", $layer->id;
-    
-        # build polylines of lines which do not already belong to a surface
-        my $polylines = $layer->make_polylines;
-        
-        # build surfaces of polylines (distinguishing contours from holes)
-        $layer->make_surfaces($polylines);
-        
-        # merge surfaces having a common line
-        $layer->merge_contiguous_surfaces;
-    }
-    
-    # detect which surfaces are near external layers
-    $print->discover_horizontal_shells;
         
     return $print;
 }
diff --git a/slic3r.pl b/slic3r.pl
index a112baf8f..0e6e15388 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -35,6 +35,7 @@ GetOptions(
     # speed options
     'print-feed-rate=i'             => \$Slic3r::print_feed_rate,
     'travel-feed-rate=i'            => \$Slic3r::travel_feed_rate,
+    'perimeter-feed-rate=i'         => \$Slic3r::perimeter_feed_rate,
     'bottom-layer-speed-ratio=f'    => \$Slic3r::bottom_layer_speed_ratio,
     
     # accuracy options
@@ -49,7 +50,9 @@ GetOptions(
     
     # retraction options
     'retract-length=f'          => \$Slic3r::retract_length,
+    'retract-speed=i'           => \$Slic3r::retract_speed,
     'retract-restart-extra=f'   => \$Slic3r::retract_restart_extra,
+    'retract-before-travel=f'   => \$Slic3r::retract_before_travel,
     
     # skirt options
     'skirts=i'              => \$Slic3r::skirts,
@@ -82,6 +85,13 @@ GetOptions(
         if $Slic3r::layer_height > $Slic3r::nozzle_diameter;
     $Slic3r::flow_width = ($Slic3r::nozzle_diameter**2) 
         * $Slic3r::thickness_ratio * PI / (4 * $Slic3r::layer_height);
+    
+    my $max_flow_width = $Slic3r::layer_height + $Slic3r::nozzle_diameter;
+    if ($Slic3r::flow_width > $max_flow_width) {
+        $Slic3r::thickness_ratio = $max_flow_width / $Slic3r::flow_width;
+        $Slic3r::flow_width = $max_flow_width;
+    }
+    
     Slic3r::debugf "Flow width = $Slic3r::flow_width\n";
     
     # --perimeters
@@ -120,7 +130,6 @@ GetOptions(
         if $Slic3r::multiply_distance < 1;
 }
 
-my $stl_parser = Slic3r::STL->new;
 my $action = 'skein';
 
 if ($action eq 'skein') {
@@ -129,7 +138,7 @@ if ($action eq 'skein') {
         if $input_file !~ /\.stl$/i;
     
     my $t0 = [gettimeofday];
-    my $print = $stl_parser->parse_file($input_file);
+    my $print = Slic3r::Print->new_from_stl($input_file);
     $print->extrude_perimeters;
     $print->remove_small_features;
     $print->extrude_fills;
@@ -172,6 +181,8 @@ Usage: slic3r.pl [ OPTIONS ] file.stl
   Speed options:
     --print-feed-rate   Speed of print moves in mm/sec (default: $Slic3r::print_feed_rate)
     --travel-feed-rate  Speed of non-print moves in mm/sec (default: $Slic3r::travel_feed_rate)
+    --perimeter-feed-rate
+                        Speed of print moves for perimeters in mm/sec (default: $Slic3r::print_feed_rate)
     --bottom-layer-speed-ratio
                         Factor to increase/decrease speeds on bottom 
                         layer by (default: $Slic3r::bottom_layer_speed_ratio)
@@ -195,6 +206,9 @@ Usage: slic3r.pl [ OPTIONS ] file.stl
     --retract-restart-extra
                         Additional amount of filament in mm to push after
                         compensating retraction (default: $Slic3r::retract_restart_extra)
+    --retract-before-travel
+                        Only retract before travel moves of this length (default: $Slic3r::retract_before_travel)
+   
    Skirt options:
     --skirts            Number of skirts to draw (default: $Slic3r::skirts)
     --skirt-distance    Distance in mm between innermost skirt and object