diff --git a/README.md b/README.md
index f8de5ae..0d707f7 100644
--- a/README.md
+++ b/README.md
@@ -5,20 +5,45 @@
 Combination of some codes and applications to create macOS installation media outside Mac app store.\
 Thanks me later :3
 
+## Motivation
+
+Honestly, the main reason is I've limited Internet. I can't download the whole 8GB, 12GB at one stroke. So, I've to download multiple times and MAS doesn't support it. Moreover, I want to save downloaded installer so that I can use them next time. That's why I made this script.
+
 ## How to Use
 
-it's still in beta. Simply, just edit `MACOS_VERSION` and `TARGET_DISK` variables and run the script.
+it's still in beta. Simply just run the script, answer the question and go!
 
-`TARGET_DISK` information can be found in `diskutil` > `table` > `Device`. In this example `disk3`. So, `TARGET_DISK` become `/dev/disk3`.
+`DISK SELECTION` information can be found in `diskutil` > `table` > `Device`. In this example `disk3`. So, `TARGET_DISK` become `/dev/disk3`.
 
 ![diskutil](screenshots/diskutil.png)
 
 ```shell script
-$ git clone https://github.com/heinthanth/macos-bootable-usb
-$ cd macos-bootable-usb
+$ curl -LO https://github.com/heinthanth/macos-bootable-usb/releases/latest/download/macos-booable-usb-creator.sh
 $ ./creator.sh
 ```
 
+Optionally, you can verify the script with this command.
+
+``` shell script
+$ curl -LO https://github.com/heinthanth/macos-bootable-usb/releases/latest/download/SHASUM
+$ shasum creator.sh -c SHASUM
+```
+
+Moreover, if you don't trust `SHASUM` file, go check with `gpg`
+
+```
+$ curl -LO https://github.com/heinthanth/macos-bootable-usb/releases/latest/download/SHASUM
+$ curl -LO https://github.com/heinthanth/macos-bootable-usb/releases/latest/download/SHASUM.gpg
+$ gpg --keyserver hkp://keys.gnupg.net --recv-key 46D4B29338EE5105BCA79A142E1082FBF9CB91E9
+$ gpg --verify SHASUM.gpg SHASUM
+```
+## Thanks
+
+Thanks to -
+
+* <https://github.com/myspaghetti/macos-virtualbox>
+* <https://github.com/kholia/OSX-KVM>
+
 ## License
 
 This work is licensed under GPLv3. See [License](LICENSE.md) for more information.
diff --git a/SHASUM b/SHASUM
new file mode 100644
index 0000000..da62a71
--- /dev/null
+++ b/SHASUM
@@ -0,0 +1 @@
+b471c68e69343b66ea45c15d518a9ce76b0e7428  creator.sh
diff --git a/SHASUM.gpg b/SHASUM.gpg
new file mode 100644
index 0000000..be304c6
Binary files /dev/null and b/SHASUM.gpg differ
diff --git a/creator.sh b/creator.sh
index dcf28c5..5b91921 100755
--- a/creator.sh
+++ b/creator.sh
@@ -108,9 +108,6 @@ else
     INSTALLATION_FILES=("BaseSystem.chunklist" "InstallInfo.plist" "AppleDiagnostics.dmg" "AppleDiagnostics.chunklist" "BaseSystem.dmg" "InstallESDDmg.pkg")
 fi
 
-# TODO: REMOVE AFTER DEVELOPMENT
-BASE_URL="http://localhost:8000"
-
 OUTPUT_DIR="${MACOS_VERSION}-files"
 mkdir -p $OUTPUT_DIR
 printf "\n"
@@ -193,10 +190,23 @@ case "$response" in
 esac
 # END OF FORMAT DISK
 
-MACOS_VERSION="catalina"
-
+# CREATION INSTALLER
 if [[ $MACOS_VERSION == "bigsur" ]]; then
-    printf "Big Sur stuffs."
+    if ! sudo -n true 2>/dev/null; then
+        printf "[*] asking for sudo passwords. "
+        sudo -v
+        printf "\n"
+    fi
+    sudo installer -pkg "${OUTPUT_DIR}/InstallAssistant.pkg" -target /
+    printf "\n"
+    sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --nointeraction --volume /Volumes/"${MACOS_VERSION}-installer/"
+    if ! sudo -n true 2>/dev/null; then
+        printf "[*] asking for sudo passwords. "
+        sudo -v
+        printf "\n"
+    fi
+    sudo chown $USER "${OUTPUT_DIR}/InstallAssistant.pkg"
+    sudo chmod 755 "${OUTPUT_DIR}/InstallAssistant.pkg"
 else
     # RESTORE DISK IMAGE
     if ! sudo -n true 2>/dev/null; then
@@ -222,3 +232,4 @@ else
 fi
 
 printf "\n[*] Installation Media \e[32mOk!\e[31m Just go reboot now!\n\n"
+# END OF CREATING INSTALLER