diff --git a/pi-eyes.sh b/pi-eyes.sh
index df25023..7bf5b40 100644
--- a/pi-eyes.sh
+++ b/pi-eyes.sh
@@ -1,30 +1,9 @@
 #!/bin/bash
 
 if [ $(id -u) -ne 0 ]; then
-	echo "Installer must be run as root."
-	echo "Try 'sudo bash $0'"
-	exit 1
-fi
-
-clear
-
-# smbus and ads1x15 Python libs are installed regardless whether ADC
-echo "This script installs software for the Adafruit"
-echo "Snake Eyes Bonnet for Raspberry Pi. Steps include:"
-echo "- Update package index files (apt-get update)"
-echo "- Install Python libraries: numpy, pi3d, svg.path,"
-echo "  rpi-gpio, python3-dev, python3-pil"
-echo "- Install Adafruit eye code and data in /boot"
-echo "- Enable SPI0 and SPI1 peripherals if needed"
-echo "- Set HDMI resolution, disable overscan"
-echo "Run time ~25 minutes. Reboot required."
-echo "EXISTING INSTALLATION, IF ANY, WILL BE OVERWRITTEN."
-echo
-echo -n "CONTINUE? [y/N] "
-read
-if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
-	echo "Canceled."
-	exit 0
+  echo "Installer must be run as root."
+  echo "Try 'sudo bash $0'"
+  exit 1
 fi
 
 # FEATURE PROMPTS ----------------------------------------------------------
@@ -38,21 +17,60 @@ INSTALL_GADGET=0
 # preceded by a number (1 to N), display a prompt, check input until
 # a valid number within the selection range is entered.
 selectN() {
-	for ((i=1; i<=$#; i++)); do
-		echo $i. ${!i}
-	done
-	echo
-	REPLY=""
-	while :
-	do
-		echo -n "SELECT 1-$#: "
-		read
-		if [[ $REPLY -ge 1 ]] && [[ $REPLY -le $# ]]; then
-			return $REPLY
-		fi
-	done
+  for ((i=1; i<=$#; i++)); do
+    echo $i. ${!i}
+  done
+  echo
+  REPLY=""
+  while :
+  do
+    echo -n "SELECT 1-$#: "
+    read
+    if [[ $REPLY -ge 1 ]] && [[ $REPLY -le $# ]]; then
+      return $REPLY
+    fi
+  done
 }
 
+clear
+
+echo "This script installs Adafruit Snake Eyes Bonnet"
+echo "software for Raspberry Pi. It's best to dedicate"
+echo "a card to this, not for systems in regular use."
+echo
+echo "Target system (may be different than current host):"
+selectN "Raspberry Pi 4, Pi 400, or Compute Module 4" "All other models"
+#if [[ $? -eq "1" ]]; then
+if [ $? -eq "1" ]; then
+  IS_PI4=1
+fi
+
+if [ $IS_PI4 ]; then
+  # Verify this is Raspbian Desktop OS (X11 should exist)
+  if [ ! -d "/usr/bin/X11" ]; then
+    echo "Target system is Pi 4/400/CM4 but this appears to"
+    echo "be a \"Lite\" OS. \"Desktop\" OS is required."
+    echo -n "Continue anyway? [y/N]"
+    read
+    if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
+      echo "Canceled."
+      exit 0
+    fi
+  fi
+else
+  # Verify this is Raspbian Lite OS (X11 should NOT exist)
+  if [ -d "/usr/bin/X11" ]; then
+    echo "Target system is not Pi 4/400/CM4 yet this appears to"
+    echo "be a \"Desktop\" OS. \"Lite\" OS (Legacy) is required."
+    echo -n "Continue anyway? [y/N]"
+    read
+    if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
+      echo "Canceled."
+      exit 0
+    fi
+  fi
+fi
+
 SCREEN_VALUES=(-o -t -i)
 SCREEN_NAMES=("OLED (128x128)" "TFT (128x128)" "IPS (240x240)" HDMI)
 RADIUS_VALUES=(128 128 240)
@@ -68,40 +86,56 @@ SCREEN_SELECT=$?
 echo -n "Install GPIO-halt utility? [y/N] "
 read
 if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
-	INSTALL_HALT=1
-	echo -n "GPIO pin for halt: "
-	read
-	HALT_PIN=$REPLY
+  INSTALL_HALT=1
+  echo -n "GPIO pin for halt: "
+  read
+  HALT_PIN=$REPLY
 fi
 
-echo -n "Install ADC support? [y/N] "
+echo -n "Install Bonnet ADC support? [y/N] "
 read
 if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
-	INSTALL_ADC=1
+  INSTALL_ADC=1
 fi
 
 echo -n "Install USB Ethernet gadget support? (Pi Zero) [y/N] "
 read
 if [[ "$REPLY" =~ (yes|y|Y)$ ]]; then
-	INSTALL_GADGET=1
+  INSTALL_GADGET=1
 fi
 
 echo
 echo "Screen type: ${SCREEN_NAMES[$SCREEN_SELECT-1]}"
 if [ $INSTALL_HALT -eq 1 ]; then
-	echo "Install GPIO-halt: YES (GPIO$HALT_PIN)"
+  echo "Install GPIO-halt: YES (GPIO$HALT_PIN)"
 else
-	echo "Install GPIO-halt: NO"
+  echo "Install GPIO-halt: NO"
 fi
-echo "ADC support: ${OPTION_NAMES[$INSTALL_ADC]}"
+echo "Bonnet ADC support: ${OPTION_NAMES[$INSTALL_ADC]}"
 echo "Ethernet USB gadget support: ${OPTION_NAMES[$INSTALL_GADGET]}"
 if [ $SCREEN_SELECT -eq 3 ]; then
-	echo "Video resolution will be set to 1280x720, no overscan"
+  echo "Video resolution will be set to 1280x720, no overscan"
 else
-	echo "Video resolution will be set to 640x480, no overscan"
+  echo "Video resolution will be set to 640x480, no overscan"
 fi
+
 echo
-echo -n "CONTINUE? [y/N] "
+echo "Installation steps include:"
+echo "- Update package index files (apt-get update)"
+echo "- Install Python libraries: numpy, pi3d, svg.path,"
+echo "  rpi-gpio, python3-dev, python3-pil"
+echo "- Install Adafruit eye code and data in /boot"
+echo "- Set HDMI resolution, GPU RAM, disable overscan"
+if [ $IS_PI4 ]; then
+	echo "- Disable desktop, configure video driver"
+fi
+echo "- Enable SPI0 and SPI1 peripherals if needed"
+echo
+echo "THIS IS A ONE-WAY OPERATION, NO UNINSTALL PROVIDED."
+echo "EXISTING INSTALLATION, IF ANY, WILL BE OVERWRITTEN."
+echo "Run time ~10 minutes. Reboot required."
+echo
+echo -n "Do you understand and want to proceed? [y/N]"
 read
 if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
 	echo "Canceled."
@@ -115,26 +149,26 @@ fi
 # perform replacement if found, else append replacement to end of file.
 # (# $1 = filename, $2 = pattern to match, $3 = replacement)
 reconfig() {
-	grep $2 $1 >/dev/null
-	if [ $? -eq 0 ]; then
-		# Pattern found; replace in file
-		sed -i "s/$2/$3/g" $1 >/dev/null
-	else
-		# Not found; append (silently)
-		echo $3 | sudo tee -a $1 >/dev/null
-	fi
+  grep $2 $1 >/dev/null
+  if [ $? -eq 0 ]; then
+    # Pattern found; replace in file
+    sed -i "s/$2/$3/g" $1 >/dev/null
+  else
+    # Not found; append (silently)
+    echo $3 | sudo tee -a $1 >/dev/null
+  fi
 }
 
 # Same as above, but appends to same line rather than new line
 reconfig2() {
-	grep $2 $1 >/dev/null
-	if [ $? -eq 0 ]; then
-		# Pattern found; replace in file
-		sed -i "s/$2/$3/g" $1 >/dev/null
-	else
-		# Not found; append to line (silently)
-                sed -i "s/$/ $3/g" $1 >/dev/null
-	fi
+  grep $2 $1 >/dev/null
+  if [ $? -eq 0 ]; then
+    # Pattern found; replace in file
+    sed -i "s/$2/$3/g" $1 >/dev/null
+  else
+    # Not found; append to line (silently)
+    sed -i "s/$/ $3/g" $1 >/dev/null
+  fi
 }
 
 echo
@@ -145,8 +179,8 @@ apt-get update
 echo "Installing Python libraries..."
 # WAS: apt-get install -y --force-yes python-pip python-dev python-imaging python-smbus
 apt-get install -y python3-pip python3-dev python3-pil python3-smbus libatlas-base-dev
-# WAS: pip3 install numpy pi3d svg.path rpi-gpio adafruit-ads1x15
-pip3 install numpy pi3d==2.34 svg.path rpi-gpio adafruit-blinka adafruit-circuitpython-ads1x15
+# WAS: pip3 install numpy pi3d==2.34 svg.path rpi-gpio adafruit-ads1x15
+pip3 install numpy pi3d svg.path rpi-gpio adafruit-blinka adafruit-circuitpython-ads1x15
 # smbus and Blinka+ADC libs are installed regardless whether ADC is
 # enabled; simplifies the Python code a little (no "uncomment this")
 
@@ -158,110 +192,165 @@ unzip master.zip
 cp -r Pi_Eyes-master /boot/Pi_Eyes
 rm -rf master.zip Pi_Eyes-master
 if [ $INSTALL_HALT -ne 0 ]; then
-	echo "Installing gpio-halt in /usr/local/bin..."
-	curl -LO https://github.com/adafruit/Adafruit-GPIO-Halt/archive/master.zip
-	unzip master.zip
-	cd Adafruit-GPIO-Halt-master
-	make
-	mv gpio-halt /usr/local/bin
-	cd ..
-	rm -rf Adafruit-GPIO-Halt-master
+  echo "Installing gpio-halt in /usr/local/bin..."
+  curl -LO https://github.com/adafruit/Adafruit-GPIO-Halt/archive/master.zip
+  unzip master.zip
+  cd Adafruit-GPIO-Halt-master
+  make
+  mv gpio-halt /usr/local/bin
+  cd ..
+  rm -rf Adafruit-GPIO-Halt-master
 fi
 
 # CONFIG -------------------------------------------------------------------
 
 echo "Configuring system..."
 
+if [ $IS_PI4 ]; then
+  # Make desktop system to boot to console (from raspi-config script):
+  systemctl set-default multi-user.target
+  ln -fs /lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@tty1.service
+  rm -f /etc/systemd/system/getty@tty1.service.d/autologin.conf
+
+  # Pi3D requires "fake" KMS overlay to work. Check /boot/config.txt for
+  # vc4-fkms-v3d overlay present and active. If so, nothing to do here,
+  # module's already configured.
+  grep '^dtoverlay=vc4-fkms-v3d' /boot/config.txt >/dev/null
+  if [ $? -ne 0 ]; then
+    # fkms overlay not present, or is commented out. Check if vc4-kms-v3d
+    # (no 'f') is present and active. That's normally the default.
+    grep '^dtoverlay=vc4-kms-v3d' /boot/config.txt >/dev/null
+    if [ $? -eq 0 ]; then
+      # It IS present. Comment out that line for posterity, and insert the
+      # 'fkms' item on the next line.
+      sed -i "s/^dtoverlay=vc4-kms-v3d/#&\ndtoverlay=vc4-fkms-v3d/g" /boot/config.txt >/dev/null
+    else
+      # It's NOT present. Silently append 'fkms' overlay to end of file.
+      echo dtoverlay=vc4-fkms-v3d | sudo tee -a /boot/config.txt >/dev/null
+    fi
+  fi
+
+  # Disable screen blanking in X config
+  echo "Section \"ServerFlags\"
+  Option \"BlankTime\" \"0\"
+  Option \"StandbyTime\" \"0\"
+  Option \"SuspendTime\" \"0\"
+  Option \"OffTime\" \"0\"
+  Option \"dpms\" \"false\"
+EndSection" > /etc/X11/xorg.conf
+
+fi
+
 # Disable overscan compensation (use full screen):
 raspi-config nonint do_overscan 1
 
+# Dedicate 128 MB to the GPU:
+sudo raspi-config nonint do_memory_split 128
+
 # HDMI settings for Pi eyes
 reconfig /boot/config.txt "^.*hdmi_force_hotplug.*$" "hdmi_force_hotplug=1"
 reconfig /boot/config.txt "^.*hdmi_group.*$" "hdmi_group=2"
 reconfig /boot/config.txt "^.*hdmi_mode.*$" "hdmi_mode=87"
 if [ $SCREEN_SELECT -eq 3 ]; then
-	# IPS display - set HDMI to 1280x720
-	reconfig /boot/config.txt "^.*hdmi_cvt.*$" "hdmi_cvt=1280 720 60 1 0 0 0"
+  # IPS display - set HDMI to 1280x720
+  reconfig /boot/config.txt "^.*hdmi_cvt.*$" "hdmi_cvt=1280 720 60 1 0 0 0"
 else
-	# All others - set HDMI to 640x480
-	reconfig /boot/config.txt "^.*hdmi_cvt.*$" "hdmi_cvt=640 480 60 1 0 0 0"
+  # All others - set HDMI to 640x480
+  reconfig /boot/config.txt "^.*hdmi_cvt.*$" "hdmi_cvt=640 480 60 1 0 0 0"
 fi
 
+
 # Enable I2C for ADC
 if [ $INSTALL_ADC -ne 0 ]; then
-	raspi-config nonint do_i2c 0
+  raspi-config nonint do_i2c 0
 fi
 
 if [ $INSTALL_HALT -ne 0 ]; then
-	# Add gpio-halt to /rc.local:
-	grep gpio-halt /etc/rc.local >/dev/null
-	if [ $? -eq 0 ]; then
-		# gpio-halt already in rc.local, but make sure correct:
-		sed -i "s/^.*gpio-halt.*$/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&/g" /etc/rc.local >/dev/null
-	else
-		# Insert gpio-halt into rc.local before final 'exit 0'
-		sed -i "s/^exit 0/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&\\nexit 0/g" /etc/rc.local >/dev/null
-	fi
+  # Add gpio-halt to /rc.local:
+  grep gpio-halt /etc/rc.local >/dev/null
+  if [ $? -eq 0 ]; then
+    # gpio-halt already in rc.local, but make sure correct:
+    sed -i "s/^.*gpio-halt.*$/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&/g" /etc/rc.local >/dev/null
+  else
+    # Insert gpio-halt into rc.local before final 'exit 0'
+    sed -i "s/^exit 0/\/usr\/local\/bin\/gpio-halt $HALT_PIN \&\\nexit 0/g" /etc/rc.local >/dev/null
+  fi
 fi
 
 # If using OLED, TFT or IPS, enable SPI and install fbx2 and eyes.py,
 # else (HDMI) skip SPI, fbx2 and install cyclops.py (single eye)
 if [ $SCREEN_SELECT -ne 4 ]; then
 
-	# Enable SPI0 using raspi-config
-	raspi-config nonint do_spi 0
+  # Enable SPI0 using raspi-config
+  raspi-config nonint do_spi 0
 
-	# Enable SPI1 by adding overlay to /boot/config.txt
-	reconfig /boot/config.txt "^.*dtparam=spi1.*$" "dtparam=spi1=on"
-	reconfig /boot/config.txt "^.*dtoverlay=spi1.*$" "dtoverlay=spi1-3cs"
+  # Enable SPI1 by adding overlay to /boot/config.txt
+  reconfig /boot/config.txt "^.*dtparam=spi1.*$" "dtparam=spi1=on"
+  reconfig /boot/config.txt "^.*dtoverlay=spi1.*$" "dtoverlay=spi1-3cs"
 
-	# Adjust spidev buffer size to 8K (default is 4K)
-	reconfig2 /boot/cmdline.txt "spidev\.bufsiz=.*" "spidev.bufsiz=8192"
+  # Adjust spidev buffer size to 8K (default is 4K)
+  reconfig2 /boot/cmdline.txt "spidev\.bufsiz=.*" "spidev.bufsiz=8192"
 
-	SCREEN_OPT=${SCREEN_VALUES[($SCREEN_SELECT-1)]}
+  SCREEN_OPT=${SCREEN_VALUES[($SCREEN_SELECT-1)]}
 
-	# Auto-start fbx2 on boot
-	grep fbx2 /etc/rc.local >/dev/null
-	if [ $? -eq 0 ]; then
-		# fbx2 already in rc.local, but make sure correct:
-		sed -i "s/^.*fbx2.*$/\/boot\/Pi_Eyes\/fbx2 $SCREEN_OPT \&/g" /etc/rc.local >/dev/null
-	else
-		# Insert fbx2 into rc.local before final 'exit 0'
-		sed -i "s/^exit 0/\/boot\/Pi_Eyes\/fbx2 $SCREEN_OPT \&\\nexit 0/g" /etc/rc.local >/dev/null
-	fi
+  # Auto-start fbx2 on boot
+  grep fbx2 /etc/rc.local >/dev/null
+  if [ $? -eq 0 ]; then
+    # fbx2 already in rc.local, but make sure correct:
+    sed -i "s/^.*fbx2.*$/\/boot\/Pi_Eyes\/fbx2 $SCREEN_OPT \&/g" /etc/rc.local >/dev/null
+  else
+    # Insert fbx2 into rc.local before final 'exit 0'
+    sed -i "s/^exit 0/\/boot\/Pi_Eyes\/fbx2 $SCREEN_OPT \&\\nexit 0/g" /etc/rc.local >/dev/null
+  fi
 
-	RADIUS=${RADIUS_VALUES[($SCREEN_SELECT-1)]}
-	# Auto-start eyes.py on boot
-	grep eyes.py /etc/rc.local >/dev/null
-	if [ $? -eq 0 ]; then
-		# eyes.py already in rc.local, but make sure correct:
-		sed -i "s/^.*eyes.py.*$/cd \/boot\/Pi_Eyes;python3 eyes.py --radius $RADIUS \&/g" /etc/rc.local >/dev/null
-	else
-		# Insert eyes.py into rc.local before final 'exit 0'
-	sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;python3 eyes.py --radius $RADIUS \&\\nexit 0/g" /etc/rc.local >/dev/null
-	fi
+  RADIUS=${RADIUS_VALUES[($SCREEN_SELECT-1)]}
+  # Auto-start eyes.py on boot
+  grep eyes.py /etc/rc.local >/dev/null
+  if [ $? -eq 0 ]; then
+    # eyes.py already in rc.local, but make sure correct:
+    if [ $IS_PI4 ]; then
+      sed -i "s/^.*eyes.py.*$/cd \/boot\/Pi_Eyes;xinit \/usr\/bin\/python3 eyes.py --radius $RADIUS \:0 \&/g" /etc/rc.local >/dev/null
+    else
+      sed -i "s/^.*eyes.py.*$/cd \/boot\/Pi_Eyes;python3 eyes.py --radius $RADIUS \&/g" /etc/rc.local >/dev/null
+    fi
+  else
+    # Insert eyes.py into rc.local before final 'exit 0'
+    if [ $IS_PI4 ]; then
+      sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;xinit \/usr\/bin\/python3 eyes.py --radius $RADIUS \:0 \&\\nexit 0/g" /etc/rc.local >/dev/null
+    else
+      sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;python3 eyes.py --radius $RADIUS \&\\nexit 0/g" /etc/rc.local >/dev/null
+    fi
+  fi
 
 else
 
-	# Auto-start cyclops.py on boot
-	grep cyclops.py /etc/rc.local >/dev/null
-	if [ $? -eq 0 ]; then
-		# cyclops.py already in rc.local, but make sure correct:
-		sed -i "s/^.*cyclops.py.*$/cd \/boot\/Pi_Eyes;python3 cyclops.py \&/g" /etc/rc.local >/dev/null
-	else
-		# Insert cyclops.py into rc.local before final 'exit 0'
-	sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;python3 cyclops.py \&\\nexit 0/g" /etc/rc.local >/dev/null
-	fi
+  # Auto-start cyclops.py on boot
+  grep cyclops.py /etc/rc.local >/dev/null
+  if [ $? -eq 0 ]; then
+    # cyclops.py already in rc.local, but make sure correct:
+    if [ $IS_PI4 ]; then
+      sed -i "s/^.*cyclops.py.*$/cd \/boot\/Pi_Eyes;xinit \/usr\/bin\/python3 cyclops.py \:0 \&/g" /etc/rc.local >/dev/null
+    else
+      sed -i "s/^.*cyclops.py.*$/cd \/boot\/Pi_Eyes;python3 cyclops.py \&/g" /etc/rc.local >/dev/null
+    fi
+  else
+    # Insert cyclops.py into rc.local before final 'exit 0'
+    if [ $IS_PI4 ]; then
+      sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;xinit \/usr\/bin\/python3 cyclops.py \:0 \&\\nexit 0/g" /etc/rc.local >/dev/null
+    else
+      sed -i "s/^exit 0/cd \/boot\/Pi_Eyes;python3 cyclops.py \&\\nexit 0/g" /etc/rc.local >/dev/null
+    fi
+  fi
 
 fi
 
 if [ $INSTALL_GADGET -ne 0 ]; then
-	reconfig /boot/config.txt "^.*dtoverlay=dwc2.*$" "dtoverlay=dwc2"
-	grep "modules-load=dwc2,g_ether" /boot/cmdline.txt >/dev/null
-	if [ $? -ne 0 ]; then
-		# Insert ethernet gadget into config.txt after 'rootwait'
-		sed -i "s/rootwait/rootwait modules-load=dwc2,g_ether/g" /boot/cmdline.txt >/dev/null
-	fi
+  reconfig /boot/config.txt "^.*dtoverlay=dwc2.*$" "dtoverlay=dwc2"
+  grep "modules-load=dwc2,g_ether" /boot/cmdline.txt >/dev/null
+  if [ $? -ne 0 ]; then
+    # Insert ethernet gadget into config.txt after 'rootwait'
+    sed -i "s/rootwait/rootwait modules-load=dwc2,g_ether/g" /boot/cmdline.txt >/dev/null
+  fi
 fi
 
 # PROMPT FOR REBOOT --------------------------------------------------------
@@ -273,8 +362,8 @@ echo
 echo -n "REBOOT NOW? [y/N] "
 read
 if [[ ! "$REPLY" =~ ^(yes|y|Y)$ ]]; then
-	echo "Exiting without reboot."
-	exit 0
+  echo "Exiting without reboot."
+  exit 0
 fi
 echo "Reboot started..."
 reboot