diff --git a/apps/gobble4/Makefile b/apps/gobble4/Makefile
new file mode 100644
index 0000000..f84e0da
--- /dev/null
+++ b/apps/gobble4/Makefile
@@ -0,0 +1,77 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   12 Sep 2010
+# Descr:  Makefile for gobble4
+
+# Definitions.
+CC = avr-gcc
+CFLAGS = -mmcu=atmega32u2 -Os -Wall -Wstrict-prototypes -Wextra -g -I../../drivers/avr -I../../drivers -I../../utils
+OBJCOPY = avr-objcopy
+SIZE = avr-size
+DEL = rm
+
+
+# Default target.
+all: gobble4.out
+
+
+# Compile: create object files from C source files.
+gobble4.o: gobble4.c ../../drivers/avr/system.h ../../drivers/avr/timer.h ../../drivers/button.h ../../drivers/display.h ../../drivers/led.h ../../utils/font.h ../../utils/pacer.h ../../utils/tinygl.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pio.o: ../../drivers/avr/pio.c ../../drivers/avr/pio.h ../../drivers/avr/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+system.o: ../../drivers/avr/system.c ../../drivers/avr/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+timer.o: ../../drivers/avr/timer.c ../../drivers/avr/system.h ../../drivers/avr/timer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+button.o: ../../drivers/button.c ../../drivers/avr/pio.h ../../drivers/avr/system.h ../../drivers/button.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+display.o: ../../drivers/display.c ../../drivers/avr/system.h ../../drivers/display.h ../../drivers/ledmat.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+led.o: ../../drivers/led.c ../../drivers/avr/pio.h ../../drivers/avr/system.h ../../drivers/led.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+ledmat.o: ../../drivers/ledmat.c ../../drivers/avr/pio.h ../../drivers/avr/system.h ../../drivers/ledmat.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+font.o: ../../utils/font.c ../../drivers/avr/system.h ../../utils/font.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pacer.o: ../../utils/pacer.c ../../drivers/avr/system.h ../../drivers/avr/timer.h ../../utils/pacer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+tinygl.o: ../../utils/tinygl.c ../../drivers/avr/system.h ../../drivers/display.h ../../utils/font.h ../../utils/tinygl.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+
+
+
+# Link: create output file (executable) from object files.
+gobble4.out: gobble4.o pio.o system.o timer.o button.o display.o led.o ledmat.o font.o pacer.o tinygl.o
+	$(CC) $(CFLAGS) $^ -o $@ -lm
+	$(SIZE) $@
+
+
+# Create hex file for programming from executable file.
+gobble4.hex: gobble4.out
+	$(OBJCOPY) -O ihex gobble4.out gobble4.hex
+
+
+# Target: clean project.
+.PHONY: clean
+clean: 
+	-$(DEL) *.o *.out *.hex
+
+
+# Target: program project.
+.PHONY: program
+program: gobble4.hex
+	dfu-programmer atmega32u2 erase; dfu-programmer atmega32u2 flash gobble4.hex; dfu-programmer atmega32u2 start
+
+
diff --git a/apps/gobble4/Makefile.test b/apps/gobble4/Makefile.test
new file mode 100644
index 0000000..b1f3c77
--- /dev/null
+++ b/apps/gobble4/Makefile.test
@@ -0,0 +1,67 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   11 Sep 2010
+# Descr:  Makefile for gobble4
+
+CC = gcc
+CFLAGS = -Wall -Wstrict-prototypes -Wextra -g -I../../drivers/test -I../../drivers -I../../utils
+
+DEL = rm
+
+
+# Default target.
+all: gobble4
+
+
+# Compile: create object files from C source files.
+gobble4-test.o: gobble4.c ../../drivers/button.h ../../drivers/display.h ../../drivers/led.h ../../drivers/test/system.h ../../drivers/test/timer.h ../../utils/font.h ../../utils/pacer.h ../../utils/tinygl.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+button-test.o: ../../drivers/button.c ../../drivers/button.h ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+display-test.o: ../../drivers/display.c ../../drivers/display.h ../../drivers/ledmat.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+led-test.o: ../../drivers/led.c ../../drivers/led.h ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+ledmat-test.o: ../../drivers/ledmat.c ../../drivers/ledmat.h ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+mgetkey-test.o: ../../drivers/test/mgetkey.c ../../drivers/test/mgetkey.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pio-test.o: ../../drivers/test/pio.c ../../drivers/test/avrtest.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+system-test.o: ../../drivers/test/system.c ../../drivers/test/avrtest.h ../../drivers/test/mgetkey.h ../../drivers/test/pio.h ../../drivers/test/system.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+timer-test.o: ../../drivers/test/timer.c ../../drivers/test/system.h ../../drivers/test/timer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+font-test.o: ../../utils/font.c ../../drivers/test/system.h ../../utils/font.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+pacer-test.o: ../../utils/pacer.c ../../drivers/test/system.h ../../drivers/test/timer.h ../../utils/pacer.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+tinygl-test.o: ../../utils/tinygl.c ../../drivers/display.h ../../drivers/test/system.h ../../utils/font.h ../../utils/tinygl.h
+	$(CC) -c $(CFLAGS) $< -o $@
+
+
+
+
+# Link: create executable file from object files.
+gobble4: gobble4-test.o button-test.o display-test.o led-test.o ledmat-test.o mgetkey-test.o pio-test.o system-test.o timer-test.o font-test.o pacer-test.o tinygl-test.o
+	$(CC) $(CFLAGS) $^ -o $@ -lrt
+
+
+# Clean: delete derived files.
+.PHONY: clean
+clean: 
+	-$(DEL) gobble4 gobble4-test.o button-test.o display-test.o led-test.o ledmat-test.o mgetkey-test.o pio-test.o system-test.o timer-test.o font-test.o pacer-test.o tinygl-test.o
+
+
+
diff --git a/apps/gobble4/doc/Makefile b/apps/gobble4/doc/Makefile
new file mode 100644
index 0000000..c93d18c
--- /dev/null
+++ b/apps/gobble4/doc/Makefile
@@ -0,0 +1,45 @@
+# File:   Makefile
+# Author: M. P. Hayes, UCECE
+# Date:   11 Sep 2010
+# Descr:  Makefile for led5 docs
+
+# The scripts used to make the graphs require the program dot; this
+# is part of the graphviz package.
+
+DEL = rm
+
+all: file_dependencies.pdf module_dependencies.pdf makefile_dependencies.pdf build_dependencies.pdf callgraph.pdf
+
+file_dependencies.pdf: files.d 
+	../../../etc/graphdeps.py $< --out $@
+
+module_dependencies.pdf: modules.d 
+	../../../etc/graphdeps.py $< --modules --rotate --out $@
+
+makefile_dependencies.pdf: ../Makefile
+	../../../etc/graphdeps.py $< --out $@
+
+build_dependencies.pdf: ../Makefile
+	../../../etc/graphdeps.py $< --out $@ --showops
+
+callgraph.pdf: callgraph.d
+	../../../etc/graphdeps.py --calls --modules $< --out $@ --showops
+
+
+files.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --relpath --files . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system.h > doc/files.d)
+
+
+modules.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --relpath --modules . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system > doc/modules.d)
+
+
+callgraph.d: ../Makefile
+	(cd ..;	../../etc/makemake.py --cc="avr-gcc" --cflags="-Os -mmcu=atmega32u2" --relpath --calls . . ../../drivers ../../drivers/avr ../../utils ../../extra --exclude system.h > doc/callgraph.d)
+
+
+# Clean: delete derived files.
+.PHONY: clean
+clean: 
+	-$(DEL) *.d *.pdf
+
diff --git a/apps/gobble4/doc/README b/apps/gobble4/doc/README
new file mode 100644
index 0000000..39a9712
--- /dev/null
+++ b/apps/gobble4/doc/README
@@ -0,0 +1,16 @@
+Running make in this directory will generate a number of PDF graphs.
+In the callgraph, the arrows means "calls".  In the dependency graphs,
+the arrows means "requires" (or "depends upon").
+
+callgraph.pdf             This shows the callgraph, i.e., what functions each
+                          function in the program calls.
+module_dependencies.pdf   This shows the dependencies between the modules.
+file_dependencies.pdf     This shows the dependencies between the files.
+makefile_dependencies.pdf This shows the dependencies required by make when
+                          building the program.
+build_dependencies.pdf    This is like makefile_dependencies.pdf but shows
+                          the operations performed to generate the new file.
+
+callgraph.d               This shows the callgraph in text format.
+files.d                   This shows the file dependencies in text format.
+modules.d                 This shows the module dependencies in text format.
diff --git a/apps/gobble4/gobble4.c b/apps/gobble4/gobble4.c
new file mode 100644
index 0000000..f8dde69
--- /dev/null
+++ b/apps/gobble4/gobble4.c
@@ -0,0 +1,275 @@
+/** @file   gobble4.c
+    @author M.P. Hayes
+    @date   28 Sep 2013
+    @brief 
+*/
+
+#include <stdlib.h>
+#include "system.h"
+#include "pacer.h"
+#include "button.h"
+#include "led.h"
+#include "timer.h"
+#include "tinygl.h"
+
+/* Number of initial objects.  */
+#define NUM_THINGS 6
+
+#define LOOP_RATE 300
+
+#define MOVE_RATE 5
+
+
+typedef struct thing_struct
+{
+    tinygl_point_t pos;
+    bool alive;
+} thing_t;
+
+
+static int8_t thing_find (thing_t *things, uint8_t num, tinygl_point_t pos)
+{
+    uint8_t i;
+
+    for (i = 0; i < num; i++)
+    {
+        if (things[i].pos.x == pos.x
+            && things[i].pos.y == pos.y
+            && things[i].alive)
+            return i;
+    }
+    return -1;
+}
+
+
+static uint8_t thing_distance_squared (thing_t *things, uint8_t this)
+{
+    int8_t dx;
+    int8_t dy;
+
+    dx = things[this].pos.x - things[0].pos.x;
+    dy = things[this].pos.y - things[0].pos.y;
+
+    return dx * dx + dy * dy;
+}
+
+
+static int8_t thing_closest (thing_t *things, uint8_t num)
+{
+    uint8_t i;
+    uint8_t which = 0;
+    uint8_t distsq = ~0;
+
+    for (i = 1; i < num; i++)
+    {
+        uint8_t distsq2;
+
+        if (!things[i].alive)
+            continue;
+
+        distsq2 = thing_distance_squared (things, i);
+        if (distsq2 < distsq)
+        {
+            distsq = distsq2;
+            which = i;
+        }
+    }
+    return which;
+}
+
+
+static void monster_move (thing_t *things, uint8_t num)
+{
+    uint8_t x;
+    uint8_t y;
+    uint8_t closest;
+    int8_t other;
+    int8_t dx;
+    int8_t dy;
+
+    closest = thing_closest (things, num);
+    
+    /* closest == 0 then no things left but the monster!  */
+
+    x = things[0].pos.x;
+    y = things[0].pos.y;
+
+    dx = things[closest].pos.x - x;
+    dy = things[closest].pos.y - y;
+
+    while (dx / 2)
+        dx = dx / 2;
+    while (dy / 2)
+        dy = dy / 2;
+
+    // printf ("%d %d %d %d %d\n", x, y, closest, dx, dy);
+
+    other = thing_find (things, num, tinygl_point (x + dx, y + dy));
+
+    if (other != -1)
+    {
+        // printf ("%d %d %d %d %d*\n", x, y, other, dx, dy);
+        things[other].alive = 0;
+    }
+
+    tinygl_draw_point (things[0].pos, 0);
+    things[0].pos.x += dx;
+    things[0].pos.y += dy;
+    tinygl_draw_point (things[0].pos, 1);
+}
+
+
+uint8_t bounds_p (tinygl_point_t pos)
+{
+    return pos.x >= 0 && pos.x < TINYGL_WIDTH
+        && pos.y >= 0 && pos.y < TINYGL_HEIGHT;    
+}
+
+
+static void thing_move (thing_t *things, uint8_t num, uint8_t this)
+{
+    uint8_t i;
+    uint8_t distsq;
+    tinygl_point_t pos;
+
+    tinygl_draw_point (things[this].pos, 0);
+
+    distsq = thing_distance_squared (things, this);
+    pos = things[this].pos;
+
+    for (i = 0; i < 12; i++)
+    {
+        int8_t dx;
+        int8_t dy;
+        tinygl_point_t newpos;
+        
+        dx = (rand () % 3) - 1;
+        dy = (rand () % 3) - 1;
+
+        newpos = tinygl_point (pos.x + dx, pos.y + dy);
+    
+        /* Check for a valid position.  */
+        if ((dx || dy) 
+            && (! bounds_p (newpos) || thing_find (things, num, newpos) != -1))
+            continue;
+
+        /* Try new position.  */
+        things[this].pos = newpos;
+
+        if (thing_distance_squared (things, this) > distsq)
+            break;
+    }
+
+    /* Stay put if cannot find better position.  */
+    if (i == 12)
+        things[this].pos = pos;
+        
+    tinygl_draw_point (things[this].pos, 1);
+}
+
+
+static void things_move (thing_t *things, uint8_t num)
+{
+    uint8_t i;
+
+    for (i = 1; i < num; i++)
+        if (things[i].alive)
+            thing_move (things, num, i);
+}
+
+
+static void things_create (thing_t *things, uint8_t num)
+{
+    uint8_t i;
+
+    things[0].pos.x = 0;
+    things[0].pos.y = 0;
+    things[0].alive = 1;
+    tinygl_draw_point (things[0].pos, 1);
+
+    for (i = 1; i < num; i++)
+    {
+        uint8_t x;
+        uint8_t y;
+
+        do
+        {
+            x = rand () % TINYGL_WIDTH;
+            y = rand () % TINYGL_HEIGHT;
+        } while (thing_find (things, i, tinygl_point (x, y)) != -1);
+        
+        things[i].pos.x = x;
+        things[i].pos.y = y;
+        things[i].alive = 1;
+
+        tinygl_draw_point (things[i].pos, 1);
+    }
+}
+
+
+static void things_destroy (thing_t *things, uint8_t num)
+{
+    uint8_t i;
+
+    for (i = 0; i < num; i++)
+    {
+        tinygl_draw_point (things[i].pos, 0);
+    }
+}
+
+
+int main (void)
+{
+    uint16_t tick = 0;
+    uint8_t running = 0;
+    thing_t things[NUM_THINGS];
+
+    system_init ();
+    button_init ();
+    led_init ();
+    led_set (LED1, 0);
+
+    tinygl_init (LOOP_RATE);
+
+    pacer_init (LOOP_RATE);
+
+    while (1)
+    {
+        uint8_t col;
+
+        /* Refresh things.  */
+        for (col = 0; col < TINYGL_WIDTH; col++)
+        {
+            pacer_wait ();
+
+            tinygl_update ();
+        }
+
+        tick++;
+        if (tick >= LOOP_RATE / MOVE_RATE)
+        {
+            tick = 0;
+
+            button_update ();
+
+            if (button_push_event_p (BUTTON1))
+            {
+                srand (timer_get ());
+                running = ! running;
+                led_set (LED1, running);
+            }
+
+            if (running)
+            {
+                things_move (things, NUM_THINGS);
+                monster_move (things, NUM_THINGS);
+            }
+            else
+            {
+                things_destroy (things, NUM_THINGS);
+                things_create (things, NUM_THINGS);
+            }
+        }
+    }
+    return 0;
+}
diff --git a/apps/stars3/stars3.c b/apps/stars3/stars3.c
index 82ddc4a..bead936 100644
--- a/apps/stars3/stars3.c
+++ b/apps/stars3/stars3.c
@@ -1,6 +1,6 @@
-/** @file   stars1.c
+/** @file   stars3.c
     @author M.P. Hayes
-    @date   25 Sep 2013
+    @date   28 Sep 2013
     @brief  Example of using pseudorandom numbers and controlling pixel
     brightness with PWM.  Note, pseudorandom numbers follow the same
     sequence.