diff --git a/README b/README
index 8336903..0c8e4a0 100644
--- a/README
+++ b/README
@@ -38,7 +38,7 @@ Requirements:
 - working C compiler
 - GNU make (probably)
 - wget
-- magick (as part of ImageMagick)
+- magick/convert (as part of ImageMagick)
 
 
 Getting started:
@@ -55,6 +55,10 @@ steaminstall_halflife.exe
 
 ...and place them alongside this README file.
 
+If you want to use your local Steam Half-Life installation,
+pass the HL_STEAM_INSTALL environment variable like so:
+`HL_STEAM_INSTALL="/path/to/Half-Life" ./start`
+
 The end result is placed into ./_build for you to copy wherever.
 
 
diff --git a/build_pak0.sh b/build_pak0.sh
index cc1191f..e9a666d 100755
--- a/build_pak0.sh
+++ b/build_pak0.sh
@@ -39,6 +39,22 @@ find_file ()
 		fi
 	done
 
+	if [ ! -z "$HL_STEAM_INSTALL" ]
+	then
+		find "$HL_STEAM_INSTALL" -type f -name "${SEARCHNAME}" | while read FOUND
+		do
+			CHECK=$(sha256sum "${FOUND}" | cut -d ' ' -f 1)
+			#echo "$CHECK == $2"
+		
+			if [ "${CHECK}" = "$2" ]
+			then
+				mkdir -p "${PAK0_OUTDIR}/$(dirname $1)"
+				cp -v "${FOUND}" "${PAK0_OUTDIR}/$1"
+				exit 0
+			fi
+		done
+	fi
+
 	if [ ! -f "${PAK0_OUTDIR}/$1" ]
 	then
 		echo "${1}" >> "./_build/missing-$3-pak0.txt"
diff --git a/dl_sources.sh b/dl_sources.sh
index 4ec0c94..cba0fda 100755
--- a/dl_sources.sh
+++ b/dl_sources.sh
@@ -30,4 +30,9 @@ fetch_resource "http://archive.org/download/Half-lifeUplink/hluplink.exe" "Half-
 fetch_resource "http://archive.org/download/half-life-patches/English/Update 1.1.1.0 English/hl1110.exe" "Half-Life: Patch 1.1.1.0"
 fetch_resource "https://archive.org/download/opfor-demo/opfordemofull.exe" "Half-Life: Opposing Force - Demo"
 fetch_resource "https://downloads.ammahls.com/HLSDK/hl_sdk_v23.exe" "Half-Life SDK v2.3"
-fetch_resource "http://archive.org/download/steaminstall_halflife/steaminstall_halflife.exe" "Steam Installer with Half-Life Cache"
\ No newline at end of file
+
+# if we pass a Steam path, skip this one
+if [ -z "$HL_STEAM_INSTALL" ]
+then
+	fetch_resource "http://archive.org/download/steaminstall_halflife/steaminstall_halflife.exe" "Steam Installer with Half-Life Cache"
+fi
\ No newline at end of file
diff --git a/rip_sources.sh b/rip_sources.sh
old mode 100755
new mode 100644
index cd79352..fb25cd3
--- a/rip_sources.sh
+++ b/rip_sources.sh
@@ -31,7 +31,11 @@ x_rewise "hluplink.exe"
 x_rewise "hl1110.exe"
 x_rewise "opfordemofull.exe"
 x_rewise "hl_sdk_v23.exe"
-x_rewise "steaminstall_halflife.exe"
+
+if [ -z "$HL_STEAM_INSTALL" ]
+then
+	x_rewise "steaminstall_halflife.exe"
+fi
 
 mkdir -p "./_tmp/hluplink-pak0"
 pakextract -o "./_tmp/hluplink-pak0" "./_tmp/hluplink.exe/MAINDIR/valve/pak0.PAK"
@@ -39,11 +43,20 @@ pakextract -o "./_tmp/hluplink-pak0" "./_tmp/hluplink.exe/MAINDIR/valve/pak0.PAK
 mkdir -p "./_tmp/opfordemofull-pak0"
 pakextract -o "./_tmp/opfordemofull-pak0" "./_tmp/opfordemofull.exe/MAINDIR/valve/pak0.PAK"
 
-mkdir -p "./_tmp/half-life.gcf"
-hlextract -p "./_tmp/steaminstall_halflife.exe/MAINDIR/SteamApps/half-life.gcf" -d "./_tmp/half-life.gcf" -e "root/valve/"
+if [ -z "$HL_STEAM_INSTALL" ]
+then
+	mkdir -p "./_tmp/half-life.gcf"
+	hlextract -p "./_tmp/steaminstall_halflife.exe/MAINDIR/SteamApps/half-life.gcf" -d "./_tmp/half-life.gcf" -e "root/valve/"
+fi
 
 ./ccase.sh -r "./_tmp"
 
 # if anything goes wrong here, it's probably imagemagick messing with the image
+if [ ! -x "$(command -v magick)" ]; then
+	convert "./_tmp/hluplink-pak0/gfx/shell/btns_main.bmp" -compress none -crop 156x4836+0+0 BMP3:"./_tmp/btns_main.bmp"
+else
+	magick "./_tmp/hluplink-pak0/gfx/shell/btns_main.bmp" -compress none -crop 156x4836+0+0 BMP3:"./_tmp/btns_main.bmp"
+fi
+
 magick "./_tmp/hluplink-pak0/gfx/shell/btns_main.bmp" -compress none -crop 156x4836+0+0 BMP3:"./_tmp/btns_main.bmp"
 bmpfix "./_tmp/hl1110.exe/maindir/valve/models/player/hgrunt/hgrunt.bmp"
\ No newline at end of file
diff --git a/start.sh b/start.sh
index e19a524..916c481 100755
--- a/start.sh
+++ b/start.sh
@@ -1,5 +1,29 @@
 #!/bin/sh
 set -e
+
+# some sanity checks before we continue
+if [ ! -x "$(command -v make)" ]; then
+	echo "make not found. Please install GNU make."
+	exit 2
+fi
+
+if [ ! -x "$(command -v cc)" ]; then
+	echo "cc not found. Please install a C compiler."
+	exit 2
+fi
+
+if [ ! -x "$(command -v wget)" ]; then
+	echo "wget not found. Please install wget."
+	exit 2
+fi
+
+if [ ! -x "$(command -v magick)" ]; then
+	if [ ! -x "$(command -v convert)" ]; then
+		echo "magick/convert not found. Please install ImageMagick or higher."
+		exit 2
+	fi
+fi
+
 ./build_tools.sh
 ./dl_sources.sh
 ./rip_sources.sh