diff --git a/allover13.c b/allover13.c
index c4dd9ba..ac8d773 100644
--- a/allover13.c
+++ b/allover13.c
@@ -12,22 +12,24 @@
  * Page 13
  */
 
-void draw_module (double x1, double y1, double side, int lastx, int lasty);
-void square_triangle (double x, double y, double side, double ht);
-void drawline (double x1, double y1, double x2, double y2);
+void draw_module(const double x, const double y, const double side, const int firstx, const int lastx, const int firsty, const int lasty);
+void square_triangle(const double x, const double y, const double side, const double ht);
+void drawline(const double wx1, const double wy1, const double wx2, const double wy2);
 
 double Scale;
 
-int main (int argc, char * const argv[])
+int main(int argc, char * const argv[])
 {
    int opt;
    int ix, iy;
    int nx, ny;
    double pitch;
-   double x1, y1;
+   double x0, y0;
+   double width, height;
+   double xoffset, yoffset;
    double maxx, maxy;
    
-   while ((opt = getopt (argc, argv, "no:p:s:t:v:")) != -1) {
+   while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {
       switch (opt) {
       case 'n':
       case 'o':
@@ -35,13 +37,13 @@ int main (int argc, char * const argv[])
       case 's':
       case 't':
       case 'v':
-         plotopt (opt, optarg);
+         plotopt(opt, optarg);
          break;
       default: /* '?' */
-         fprintf (stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n",
+         fprintf(stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n",
                   argv[0]);
-         fprintf (stderr, "       <size> ::= A1 | A2 | A3 | A4 | A5\n");
-         exit (EXIT_FAILURE);
+         fprintf(stderr, "       <size> ::= A1 | A2 | A3 | A4 | A5\n");
+         exit(EXIT_FAILURE);
       }
    }
 
@@ -51,120 +53,151 @@ int main (int argc, char * const argv[])
    Scale = 40.0;
    pitch = 45.0 * Scale;
    
-   plotbegin (1);
+   plotbegin(0);
 
-   getplotsize (&maxx, &maxy);
+   getplotsize(&maxx, &maxy);
+   
+   width = nx * pitch;
+   height = ny * pitch;
+   
+   xoffset = (maxx - width) / 2.0;
+   yoffset = (maxy - height) / 2.0;
+   
+   rectangle(xoffset, yoffset, xoffset + width, yoffset + height);
    
    for (ix = 0; ix < nx; ix++) {
       for (iy = 0; iy < ny; iy++) {
-         x1 = (double)ix * pitch;
-         y1 = (double)iy * pitch;
-         draw_module (x1, y1, pitch, ix == nx - 1, iy == ny - 1);
+         x0 = xoffset + ((double)ix * pitch);
+         y0 = yoffset + ((double)iy * pitch);
+         draw_module(x0, y0, pitch, ix == 0, ix == nx - 1, iy == 0, iy == ny - 1);
       }
    }
 
-   plotend ();
+   plotend();
    
    return (0);
 }
 
 
-void draw_module (double x, double y, double side, int lastx, int lasty)
+void draw_module(const double x, const double y, const double side, const int firstx, const int lastx, const int firsty, const int lasty)
 {
    int i;
-   double radius;
-   double offset;
    double trueside;
-   double step = 5.5 * Scale;
+   const double step = 5.5 * Scale;
+   const double radius = sqrt ((step * step) + (step * step));
    double hside = side / 2.0;
+   double offset = 3.0 * step;
    
-   offset = (double)3 * step;
-   
-   drawline (x + offset, y + hside, x + side - offset, y + hside);
-   drawline (x + hside, y + offset, x + hside, y + side - offset);
+   drawline(x + offset, y + hside, x + side - offset, y + hside);
+   drawline(x + hside, y + offset, x + hside, y + side - offset);
    
    for (i = 0; i < 3; i++) {
       offset = (double)(i + 1) * step;
       trueside = side - (2.0 * step * (double)(i + 1));
-      square_triangle (x + offset, y + offset, trueside, step);
+      square_triangle(x + offset, y + offset, trueside, step);
    }
    
-   radius = sqrt ((step * step) + (step * step));
-   
-   circle (x, y, radius);
-   
-   if (lastx)
-      circle (x + side, y, radius);
-      
-   if (lasty)
-      circle (x, y + side, radius);
-      
-   if (lastx && lasty)
-      circle (x + side, y + side, radius);
+   if (firsty) {
+      moveto(x + radius, y);
+      lineto(x + radius, y);
+      if (firstx)
+         arc(x, y, 90.0);
+      else
+         arc(x, y, 180.0);
+   }
+   else if (firstx) {
+      moveto(x, y - radius);
+      lineto(x, y - radius);
+      arc(x, y, 180.0);
+   }
+   else
+      circle(x, y, radius);
+   
+   if (lastx) {
+      moveto(x + side, y + radius);
+      lineto(x + side, y + radius);
+      if (firsty)
+         arc(x + side, y, 90.0);
+      else
+         arc(x + side, y, 180.0);
+   }
+
+   if (lasty) {
+      if (firstx) {
+         moveto(x, y + side - radius);
+         lineto(x, y + side - radius);
+         arc(x, y + side, 90.0);
+      }
+      else {
+         moveto(x - radius, y + side);
+         lineto(x - radius, y + side);
+         arc(x, y + side, 180.0);
+      }
+   }
+
+   if (lastx && lasty) {
+      moveto(x + side - radius, y + side);
+      lineto(x + side - radius, y + side);
+      arc(x + side, y + side, 90.0);
+   }
 }
 
 
-void square_triangle (double x, double y, double side, double ht)
+void square_triangle(const double x, const double y, const double side, const double ht)
 {
-   double hside;
+   const double hside = side / 2.0;
    
-   rectangle (x, y, x + side, y + side);
+   rectangle(x, y, x + side, y + side);
 
-   hside = side / 2.0;
-   
-   moveto (x, y);
-   lineto (x - ht, y + hside);
-   lineto (x, y + side);
-   lineto (x + hside, y + ht + side);
-   lineto (x + side, y + side);
-   lineto (x + side + ht, y + hside);
-   lineto (x + side, y);
-   lineto (x + hside, y - ht);
-   lineto (x, y);
+   moveto(x, y);
+   lineto(x - ht, y + hside);
+   lineto(x, y + side);
+   lineto(x + hside, y + ht + side);
+   lineto(x + side, y + side);
+   lineto(x + side + ht, y + hside);
+   lineto(x + side, y);
+   lineto(x + hside, y - ht);
+   lineto(x, y);
 }
 
 
-void drawline (double wx1, double wy1, double wx2, double wy2)
+void drawline(const double wx1, const double wy1, const double wx2, const double wy2)
 {
    static int cx = -32767, cy = -32767;
    static double wcx = -1.0, wcy = -1.0;
    int x1, y1, x2, y2;
-   double dx1, dy1, dx2, dy2;
-   double d1, d2;
+   const double dx1 = wx1 - wcx;
+   const double dy1 = wy1 - wcy;
+   const double dx2 = wx2 - wcx;
+   const double dy2 = wy2 - wcy;
+   const double d1 = sqrt((dx1 * dx1) + (dy1 * dy1));
+   const double d2 = sqrt((dx2 * dx2) + (dy2 * dy2));
    char hpgl[32];
    
-   dx1 = wx1 - wcx;
-   dy1 = wy1 - wcy;
-   dx2 = wx2 - wcx;
-   dy2 = wy2 - wcy;
-   
-   d1 = sqrt ((dx1 * dx1) + (dy1 * dy1));
-   d2 = sqrt ((dx2 * dx2) + (dy2 * dy2));
-   
    if (d1 < d2) {
-      x1 = getdevx (wx1);
-      y1 = getdevy (wy1);
-      x2 = getdevx (wx2);
-      y2 = getdevy (wy2);
+      x1 = getdevx(wx1);
+      y1 = getdevy(wy1);
+      x2 = getdevx(wx2);
+      y2 = getdevy(wy2);
       wcx = wx2;
       wcy = wy2;
    }
    else {
-      x1 = getdevx (wx2);
-      y1 = getdevy (wy2);
-      x2 = getdevx (wx1);
-      y2 = getdevy (wy1);
+      x1 = getdevx(wx2);
+      y1 = getdevy(wy2);
+      x2 = getdevx(wx1);
+      y2 = getdevy(wy1);
       wcx = wx1;
       wcy = wy1;
    }
    
    if ((cx != x1) || (cy != y1)) {
-      snprintf (hpgl, 32, "\nPU;PA%d,%d;", x1, y1);
-      hpglout (hpgl);
+      snprintf(hpgl, sizeof (hpgl), "\nPU;PA%d,%d;", x1, y1);
+      hpglout(hpgl);
    }
-      
-   snprintf (hpgl, 32, "PD;PA%d,%d;", x2, y2);   
-   hpglout (hpgl);
+
+   snprintf(hpgl, sizeof (hpgl), "PD;PA%d,%d;", x2, y2);
+   hpglout(hpgl);
    
    cx = x2;
    cy = y2;