diff --git a/root/etc/s6-overlay/s6-rc.d/svc-de/run b/root/etc/s6-overlay/s6-rc.d/svc-de/run
index bf6a826..dcdf0ae 100755
--- a/root/etc/s6-overlay/s6-rc.d/svc-de/run
+++ b/root/etc/s6-overlay/s6-rc.d/svc-de/run
@@ -8,11 +8,21 @@ while true; do
   sleep .5
 done
 
-# set sane resolution before starting apps
-if ! s6-setuidgid abc xrandr | grep -q "1024x768"; then
-  s6-setuidgid abc xrandr --newmode "1024x768" 63.50  1024 1072 1176 1328  768 771 775 798 -hsync +vsync
-  s6-setuidgid abc xrandr --addmode screen "1024x768"
-  s6-setuidgid abc xrandr --output screen --mode "1024x768" --dpi 96
+# set resolution before starting apps
+# Use environment variables if set, otherwise default to 1024x768
+RESOLUTION_WIDTH=${SELKIES_MANUAL_WIDTH:-1024}
+RESOLUTION_HEIGHT=${SELKIES_MANUAL_HEIGHT:-768}
+RESOLUTION="${RESOLUTION_WIDTH}x${RESOLUTION_HEIGHT}"
+
+# Generate modeline using cvt
+MODELINE=$(s6-setuidgid abc cvt ${RESOLUTION_WIDTH} ${RESOLUTION_HEIGHT} | grep "Modeline" | sed 's/^.*Modeline //')
+MODELINE_NAME=$(echo "$MODELINE" | cut -d' ' -f1 | tr -d '"')
+MODELINE_PARAMS=$(echo "$MODELINE" | cut -d' ' -f2-)
+
+if ! s6-setuidgid abc xrandr | grep -q "$RESOLUTION"; then
+  s6-setuidgid abc xrandr --newmode $MODELINE
+  s6-setuidgid abc xrandr --addmode screen "$MODELINE_NAME"
+  s6-setuidgid abc xrandr --output screen --mode "$MODELINE_NAME" --dpi 96
 fi
 
 # set xresources