diff --git a/calculator/.gitignore b/.gitignore
similarity index 91%
rename from calculator/.gitignore
rename to .gitignore
index c02afb2..f6c30e2 100644
--- a/calculator/.gitignore
+++ b/.gitignore
@@ -44,6 +44,7 @@ lib64/
 parts/
 sdist/
 var/
+*.dist-info/
 *.egg-info/
 .installed.cfg
 *.egg
@@ -57,10 +58,5 @@ var/
 ## mpeltonen/sbt-idea plugin
 .idea_modules/
 
-# Briefcase build directories
-iOS/
-macOS/
-windows/
-android/
-linux/
-django/
+# Briefcase log files
+logs/
diff --git a/calculator/src/calculator/__init__.py b/CHANGELOG
similarity index 100%
rename from calculator/src/calculator/__init__.py
rename to CHANGELOG
diff --git a/calculator/LICENSE b/LICENSE
similarity index 100%
rename from calculator/LICENSE
rename to LICENSE
diff --git a/calculator/README.rst b/README.rst
similarity index 100%
rename from calculator/README.rst
rename to README.rst
diff --git a/calculator/pyproject.toml b/calculator/pyproject.toml
deleted file mode 100644
index 5eae34c..0000000
--- a/calculator/pyproject.toml
+++ /dev/null
@@ -1,49 +0,0 @@
-[tool.briefcase]
-project_name = "Calculator"
-bundle = "com.abirshandilya.calculator"
-version = "0.0.1"
-url = "https://abirshandilya.com/calculator"
-license = "BSD license"
-author = 'Abir Shandilya'
-author_email = "abirshandilya@gmail.com"
-
-[tool.briefcase.app.calculator]
-formal_name = "Calculator"
-description = "A basic calculator beeware application"
-icon = "src/calculator/resources/calculator"
-sources = ['src/calculator']
-requires = []
-
-
-[tool.briefcase.app.calculator.macOS]
-requires = [
-    'toga-cocoa>=0.3.0.dev20',
-]
-
-[tool.briefcase.app.calculator.linux]
-requires = [
-    'toga-gtk>=0.3.0.dev20',
-]
-system_requires = [
-    'libgirepository1.0-dev',
-    'libcairo2-dev',
-    'libpango1.0-dev',
-    'libwebkitgtk-3.0-0',
-    'gir1.2-webkit-3.0',
-]
-
-[tool.briefcase.app.calculator.windows]
-requires = [
-    'toga-winforms>=0.3.0.dev20',
-]
-
-# Mobile deployments
-[tool.briefcase.app.calculator.iOS]
-requires = [
-    'toga-iOS>=0.3.0.dev20',
-]
-
-[tool.briefcase.app.calculator.android]
-requires = [
-    'toga-android>=0.3.0.dev20',
-]
diff --git a/calculator/src/calculator.dist-info/INSTALLER b/calculator/src/calculator.dist-info/INSTALLER
deleted file mode 100644
index 0d8da94..0000000
--- a/calculator/src/calculator.dist-info/INSTALLER
+++ /dev/null
@@ -1 +0,0 @@
-briefcase
diff --git a/calculator/src/calculator.dist-info/METADATA b/calculator/src/calculator.dist-info/METADATA
deleted file mode 100644
index aafb757..0000000
--- a/calculator/src/calculator.dist-info/METADATA
+++ /dev/null
@@ -1,10 +0,0 @@
-Metadata-Version: 2.1
-Briefcase-Version: 0.3.5
-Name: calculator
-Formal-Name: Calculator
-App-ID: com.abirshandilya.calculator.calculator
-Version: 0.0.1
-Home-page: https://abirshandilya.com/calculator
-Author: Abir Shandilya
-Author-email: abirshandilya@gmail.com
-Summary: A basic calculator beeware application
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..d13eb20
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,149 @@
+[tool.briefcase]
+project_name = "Calculator"
+bundle = "com.abirshandilya.calculator"
+version = "0.0.1"
+url = "https://abirshandilya.com/calculator"
+license = "BSD license"
+author = 'Abir Shandilya'
+author_email = "abirshandilya@gmail.com"
+
+[tool.briefcase.app.calculator]
+formal_name = "Calculator"
+description = "A basic calculator beeware application"
+long_description = """More details about the app should go here.
+"""
+icon = "src/calculator/resources/calculator"
+sources = ['src/calculator',]
+test_sources = [
+    "tests",
+]
+requires = []
+test_requires = [
+    "pytest",
+]
+
+
+[tool.briefcase.app.calculator.macOS]
+requires = [
+    "toga-cocoa~=0.4.8",
+    "std-nslog~=1.0.0"
+]
+
+[tool.briefcase.app.calculator.linux]
+requires = [
+    "toga-gtk~=0.4.8",
+]
+
+[tool.briefcase.app.calculator.linux.system.debian]
+system_requires = [
+    # Needed to compile pycairo wheel
+    "libcairo2-dev",
+    # Needed to compile PyGObject wheel
+    "libgirepository1.0-dev",
+]
+
+system_runtime_requires = [
+    # Needed to provide GTK
+    "libgtk-3-0",
+    # Needed to provide GI bindings to GTK
+    "libgirepository-1.0-1",
+    "gir1.2-gtk-3.0",
+    # Needed to provide WebKit2 at runtime
+    # "libwebkit2gtk-4.0-37",
+    # "gir1.2-webkit2-4.0",
+]
+
+[tool.briefcase.app.calculator.linux.system.rhel]
+system_requires = [
+    # Needed to compile pycairo wheel
+    "cairo-gobject-devel",
+    # Needed to compile PyGObject wheel
+    "gobject-introspection-devel",
+]
+
+system_runtime_requires = [
+    # Needed to support Python bindings to GTK
+    "gobject-introspection",
+    # Needed to provide GTK
+    "gtk3",
+    # Needed to provide WebKit2 at runtime
+    # "webkit2gtk3",
+]
+
+[tool.briefcase.app.calculator.linux.system.arch]
+system_requires = [
+    # Needed to compile pycairo wheel
+    "cairo",
+    # Needed to compile PyGObject wheel
+    "gobject-introspection",
+    # Runtime dependencies that need to exist so that the
+    # Arch package passes final validation.
+    # Needed to provide GTK
+    "gtk3",
+    # Dependencies that GTK looks for at runtime
+    "libcanberra",
+    # Needed to provide WebKit2
+    # "webkit2gtk",
+]
+
+system_runtime_requires = [
+    # Needed to provide GTK
+    "gtk3",
+    # Needed to provide PyGObject bindings
+    "gobject-introspection-runtime",
+    # Dependencies that GTK looks for at runtime
+    "libcanberra",
+    # Needed to provide WebKit2 at runtime
+    # "webkit2gtk",
+]
+
+[tool.briefcase.app.calculator.linux.appimage]
+manylinux = "manylinux2014"
+
+system_requires = [
+    # Needed to compile pycairo wheel
+    "cairo-gobject-devel",
+    # Needed to compile PyGObject wheel
+    "gobject-introspection-devel",
+    # Needed to provide GTK
+    "gtk3-devel",
+    # Dependencies that GTK looks for at runtime, that need to be
+    # in the build environment to be picked up by linuxdeploy
+    "libcanberra-gtk3",
+    "PackageKit-gtk3-module",
+    "gvfs-client",
+    # Needed to provide WebKit2 at runtime
+    # "webkit2gtk3",
+]
+linuxdeploy_plugins = [
+    "DEPLOY_GTK_VERSION=3 gtk",
+]
+
+[tool.briefcase.app.calculator.linux.flatpak]
+flatpak_runtime = "org.gnome.Platform"
+flatpak_runtime_version = "44"
+flatpak_sdk = "org.gnome.Sdk"
+
+[tool.briefcase.app.calculator.windows]
+requires = [
+    "toga-winforms~=0.4.8",
+]
+
+# Mobile deployments
+[tool.briefcase.app.calculator.iOS]
+requires = [
+    "toga-iOS~=0.4.8",
+    "std-nslog~=1.0.0"
+]
+
+[tool.briefcase.app.calculator.android]
+requires = [
+    "toga-android~=0.4.8"
+]
+
+# Web deployments
+[tool.briefcase.app.calculator.web]
+requires = [
+    "toga-web~=0.4.8",
+]
+style_framework = "Shoelace v2.3"
diff --git a/calculator/src/calculator/resources/__init__.py b/src/calculator/__init__.py
similarity index 100%
rename from calculator/src/calculator/resources/__init__.py
rename to src/calculator/__init__.py
diff --git a/calculator/src/calculator/__main__.py b/src/calculator/__main__.py
similarity index 100%
rename from calculator/src/calculator/__main__.py
rename to src/calculator/__main__.py
diff --git a/calculator/src/calculator/app.py b/src/calculator/app.py
similarity index 98%
rename from calculator/src/calculator/app.py
rename to src/calculator/app.py
index 2ef7d01..eaea97a 100644
--- a/calculator/src/calculator/app.py
+++ b/src/calculator/app.py
@@ -108,6 +108,8 @@ def enterdata(self,widget,number):
 
     def calculate(self,widget):
         output = eval(self.input_text.value)
+        if output == "":
+            output = "ERROR!"
         self.input_text.value = output
 def main():
     return Calculator()
diff --git a/src/calculator/resources/__init__.py b/src/calculator/resources/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/calculator/src/calculator/resources/calculator.icns b/src/calculator/resources/calculator.icns
similarity index 100%
rename from calculator/src/calculator/resources/calculator.icns
rename to src/calculator/resources/calculator.icns
diff --git a/calculator/src/calculator/resources/calculator.ico b/src/calculator/resources/calculator.ico
similarity index 100%
rename from calculator/src/calculator/resources/calculator.ico
rename to src/calculator/resources/calculator.ico
diff --git a/calculator/src/calculator/resources/calculator.png b/src/calculator/resources/calculator.png
similarity index 100%
rename from calculator/src/calculator/resources/calculator.png
rename to src/calculator/resources/calculator.png