diff --git a/ptrude/Makefile b/ptrude/Makefile
index 8b92aae..c85c38a 100644
--- a/ptrude/Makefile
+++ b/ptrude/Makefile
@@ -1,13 +1,66 @@
-CFLAGS = -Wall -g
+#
+# Makefile - Makefile of ptrude
+#
+# Written 2011 by Werner Almesberger
+# Copyright 2011 by Werner Almesberger
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+
+SHELL = /bin/bash
+
+MAIN = ptrude
+OBJS = $(MAIN).o path.o
+
+CFLAGS = -Wall -g -Wshadow -Wmissing-prototypes \
+         -Wmissing-declarations -Wno-format-zero-length
 LDFLAGS = -lm
-OBJS = ptrude.o path.o
 
-.PHONY:	clean try
+# ----- Verbosity control -----------------------------------------------------
 
-ptrude:	$(OBJS)
+CC_normal	:= $(CC)
+DEPEND_normal	:= $(CPP) $(CFLAGS) -MM -MG
 
-try:	ptrude
-	./ptrude <try | tee out
+CC_quiet	= @echo "  CC       " $@ && $(CC_normal)
+DEPEND_quiet	= @$(DEPEND_normal)
+
+ifeq ($(V),1)
+    CC		= $(CC_normal)
+    DEPEND	= $(DEPEND_normal)
+else
+    CC		= $(CC_quiet)
+    DEPEND	= $(DEPEND_quiet)
+endif
+
+# ----- Rules -----------------------------------------------------------------
+
+.PHONY:		clean try
+
+$(MAIN):		$(OBJS)
+
+try:		$(MAIN)
+		./$(MAIN) <try | tee out
 
 clean:
-	rm -f $(OBJS)
+		rm -f $(OBJS) $(OBJS:.o=.d)
+
+spotless:	clean
+		rm -f $(MAIN)
+
+# ----- Dependencies ----------------------------------------------------------
+
+# compile and generate dependencies, from fped, based on
+# http://scottmcpeak.com/autodepend/autodepend.html
+
+%.o:		%.c
+		$(CC) -c $(CFLAGS) $*.c -o $*.o
+		$(DEPEND) $*.c | \
+		  sed -e \
+		    '/^\(.*:\)\? */{p;s///;s/ *\\\?$$/ /;s/  */:\n/g;H;}' \
+		    -e '$${g;p;}' -e d >$*.d; \
+		  [ "$${PIPESTATUS[*]}" = "0 0" ] || { rm -f $*.d; exit 1; }
+
+-include $(OBJS:.o=.d)
diff --git a/ptrude/path.c b/ptrude/path.c
index e7b8476..a9f14f8 100644
--- a/ptrude/path.c
+++ b/ptrude/path.c
@@ -1,3 +1,15 @@
+/*
+ * path.c - 2D path operations
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -92,6 +104,13 @@ static const struct vertex *add_vertex(struct path *path, double x, double y,
 }
 
 
+/*
+ * "corner" replaces a corner with a ploygon if the corner is too sharp to
+ * be within distance "d" of the bend radius. This may change the point from
+ * where we resume drawing (originally the corner point, "b"). "corner"
+ * therefore returns the new end of the arc.
+ */
+
 static const struct vertex *corner(struct path *path, const struct vertex *a,
     const struct vertex *b, const struct vertex *c, double r, double d)
 {
@@ -230,17 +249,29 @@ static const struct vertex *corner(struct path *path, const struct vertex *a,
 		n = (int) ceil((t2-2*(p+q))/(2*q));
 
 		/*
-		 * @@@ We should evenly distribute the slack and try to pick a
+		 * We could evenly distribute the slack and try to pick a
 		 * smaller value for d, but that seems difficult.
 		 *
+		 * A drawback of reducing p would be that we may make the
+		 * corner unnecessarily sharp, possibly even turning against
+		 * the general direction of the turn. We'd still respect the
+		 * bend radius and the tolerance, but the result may look weird
+		 * anyway.
+		 *
 		 * For now, we just center the polygon.
 		 */
 		q = (t2/2-p)/(n+1);
 
 		if (n)
 			ang = p+q;
-		else
+		else {
 			ang = t2/2;
+			/*
+			 * @@@ To do: adjust the radius such that we always hug
+			 * the r-d circle (see arc.fig) and usually not the
+			 * r+d circle. Right now, it's just the opposite.
+			 */
+		}
 
 		u = tan(p)*(r-d);
 		v = tan(q)*(r-d);
diff --git a/ptrude/path.h b/ptrude/path.h
index 8215298..5410c27 100644
--- a/ptrude/path.h
+++ b/ptrude/path.h
@@ -1,3 +1,15 @@
+/*
+ * path.h - 2D path operations
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
 #ifndef PATH_H
 #define PATH_H
 
diff --git a/ptrude/ptrude.c b/ptrude/ptrude.c
index 6df85ff..dff3533 100644
--- a/ptrude/ptrude.c
+++ b/ptrude/ptrude.c
@@ -1,3 +1,15 @@
+/*
+ * ptrude.c - Extrusion of a 2D path along a perpendicular 2D path
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
 #include <stdio.h>
 
 #include "path.h"