diff --git a/README.md b/README.md
index e31742a..7a1790e 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,5 @@
-# ESEF (ElasticSearch Explain Formatter)
+# ESEF
+*ElasticSearch Explain (API) Formatter*
 
 ## Build project locally
 ```shell script
@@ -8,3 +9,6 @@
 
 fyne package -os darwin # optional: -icon icon.png
 ```
+
+## Credits
+The app icon is from the [Material Icon Set](https://material.io/resources/icons/?search=tree&icon=account_tree&style=baseline).
diff --git a/esef.go b/esef.go
index 938725a..b7d959e 100644
--- a/esef.go
+++ b/esef.go
@@ -1,15 +1,15 @@
 package main
 
 import (
-	"fmt"
-
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/app"
 	"fyne.io/fyne/v2/container"
 	"fyne.io/fyne/v2/widget"
+
+	"./util"
 )
 
-const APP_TITLE = "ESEF v0.1-alpha"
+const AppTitle = "ESEF v0.2"
 const CopiedOutputToClipboardMessageText = "Copied output to clipboard!"
 const InputLabelText = "Input"
 const OutputLabelText = "Output"
@@ -31,7 +31,7 @@ func main() {
 
 func buildMainWindow() fyne.Window {
 	application := app.New()
-	Window = application.NewWindow(APP_TITLE)
+	Window = application.NewWindow(AppTitle)
 
 	Window.SetContent(container.NewBorder(
 		nil,
@@ -47,15 +47,17 @@ func buildMainWindow() fyne.Window {
 	return Window
 }
 
-func buildFormatArea() *fyne.Container {
-	return container.NewAdaptiveGrid(
-		2,
-		widget.NewButton(SimpleFormatButtonText, func() {
-			handleSimpleFormatButtonClick()
-		}),
-		widget.NewButton(TreeFormatButtonText, func() {
-			handleTreeFormatButtonClick()
-		}),
+func buildFormatArea() *widget.Card {
+	return widget.NewCard("Format", "",
+		container.NewAdaptiveGrid(
+			2,
+			widget.NewButton(SimpleFormatButtonText, func() {
+				handleSimpleFormatButtonClick()
+			}),
+			widget.NewButton(TreeFormatButtonText, func() {
+				handleTreeFormatButtonClick()
+			}),
+		),
 	)
 }
 
@@ -75,35 +77,36 @@ func handleTreeFormatButtonClick() {
 	OutputEntry.SetText(formatInput(true))
 }
 
-func buildOutputArea() *fyne.Container {
+func buildOutputArea() *widget.Card {
 	OutputEntry = widget.NewMultiLineEntry()
 
 	OutputLabel = widget.NewLabel(OutputLabelText)
 	OutputLabel.Alignment = fyne.TextAlignCenter
 
-	return container.NewBorder(
-		OutputLabel,
-		widget.NewButton(CopyButtonText, func() {
-			handleCopyOutputButtonClick()
-		}),
-		nil,
-		nil,
-		OutputEntry,
+	return widget.NewCard(
+		OutputLabelText,
+		"",
+		container.NewBorder(
+			nil,
+			widget.NewButton(CopyButtonText, func() {
+				handleCopyOutputButtonClick()
+			}),
+			nil,
+			nil,
+			OutputEntry,
+		),
 	)
 }
 
-func buildInputArea() *fyne.Container {
+func buildInputArea() *widget.Card {
 	InputEntry = widget.NewMultiLineEntry()
-	InputEntry.Text = GetExplainApiOutputExample()
 
 	InputLabel = widget.NewLabel(InputLabelText)
 	InputLabel.Alignment = fyne.TextAlignCenter
 
-	return container.NewBorder(
-		InputLabel,
-		nil,
-		nil,
-		nil,
+	return widget.NewCard(
+		InputLabelText,
+		"",
 		InputEntry,
 	)
 }
@@ -114,19 +117,22 @@ func handleCopyOutputButtonClick() {
 }
 
 func formatInput(useTreeFormat bool) string {
-	explainApiDocument := ExtractDataFromExplainAPI(InputEntry.Text)
 	var formattedString string
+	explainApiDocument, err := util.ExtractDataFromExplainAPI(InputEntry.Text)
+
+	if err != nil {
+		return err.Error()
+	}
 
 	if useTreeFormat {
-		formattedString = FormatExplainApiDocument(explainApiDocument, useTreeFormat)
+		formattedString = util.FormatExplainApiDocument(explainApiDocument, useTreeFormat)
 	} else {
-		formattedString = FormatExplainApiDocument(explainApiDocument, useTreeFormat)
+		formattedString = util.FormatExplainApiDocument(explainApiDocument, useTreeFormat)
 	}
 
-	fmt.Println(formattedString)
 	return formattedString
 }
 
 func sendOSNotification(message string) {
-	fyne.CurrentApp().SendNotification(fyne.NewNotification(APP_TITLE, message))
+	fyne.CurrentApp().SendNotification(fyne.NewNotification(AppTitle, message))
 }
diff --git a/icon.png b/icon.png
new file mode 100644
index 0000000..e43a2bc
Binary files /dev/null and b/icon.png differ
diff --git a/extractor.go b/util/extractor.go
similarity index 62%
rename from extractor.go
rename to util/extractor.go
index 41d3ec6..bc77b33 100644
--- a/extractor.go
+++ b/util/extractor.go
@@ -1,9 +1,12 @@
-package main
+package util
 
 import (
 	"encoding/json"
+	"errors"
 )
 
+const ErrorMessage = "error during JSON Data extraction\n\nplease check your input string for any json errors"
+
 type ExplainAPIDocument struct {
 	Index       string      `json:"_index"`
 	Type        string      `json:"_type"`
@@ -18,18 +21,18 @@ type ExplainNode struct {
 	Details     []ExplainNode `json:"details"`
 }
 
-func ExtractDataFromExplainAPI(explainAPIOutput string) ExplainAPIDocument {
+func ExtractDataFromExplainAPI(explainAPIOutput string) (ExplainAPIDocument, error) {
 	return extractDocumentFromJson(explainAPIOutput)
 }
 
-func extractDocumentFromJson(inputJson string) ExplainAPIDocument {
+func extractDocumentFromJson(inputJson string) (ExplainAPIDocument, error) {
 	var explainAPIDocument ExplainAPIDocument
 	byteData := []byte(inputJson)
 	err := json.Unmarshal(byteData, &explainAPIDocument)
 
 	if err != nil {
-		return ExplainAPIDocument{}
+		return ExplainAPIDocument{}, errors.New(ErrorMessage)
 	}
 
-	return explainAPIDocument
+	return explainAPIDocument, nil
 }
diff --git a/formatter.go b/util/formatter.go
similarity index 93%
rename from formatter.go
rename to util/formatter.go
index 9e8b4c4..ece1d0e 100644
--- a/formatter.go
+++ b/util/formatter.go
@@ -1,4 +1,4 @@
-package main
+package util
 
 import (
 	"fmt"
@@ -14,6 +14,7 @@ const LShape = "└─ "
 const EmptyStartString = ""
 
 const DocumentInfoHeaderFormat = "index: %s\ndocumentId: %s\nmatched: %t\nexplanation:\n%s"
+const ExplainNoteFormat = "%s%s%f (%s)\n"
 
 func FormatExplainApiDocument(doc ExplainAPIDocument, useTreeFormat bool) string {
 	var formattedExplanation string
@@ -51,7 +52,7 @@ func formatExplainNodesToTreeFormat(previousIndentation string, isRootNode bool,
 		isLastInTreeLevel := isLastInTreeLevel(i, numberOfNodes)
 		lineSymbol := getLineSymbol(isLastInTreeLevel, isRootNode)
 
-		result += fmt.Sprintf("%s%s%f (%s)\n", previousIndentation, lineSymbol, node.Value, node.Description)
+		result += fmt.Sprintf(ExplainNoteFormat, previousIndentation, lineSymbol, node.Value, node.Description)
 
 		if len(node.Details) > 0 {
 			newIndentation := createNewIndentation(previousIndentation, isRootNode, isLastInTreeLevel)