diff --git a/.gitignore b/.gitignore
index a1c2a23..438d538 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+ProfCalculator/.classpath
+.project
 # Compiled class file
 *.class
 
@@ -21,3 +23,101 @@
 
 # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
 hs_err_pid*
+
+
+# Created by https://www.toptal.com/developers/gitignore/api/java,eclipse
+# Edit at https://www.toptal.com/developers/gitignore?templates=java,eclipse
+
+### Eclipse ###
+.metadata
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/*
+.loadpath
+.recommenders
+
+# External tool builders
+.externalToolBuilders/
+
+# Locally stored "Eclipse launch configurations"
+*.launch
+
+# PyDev specific (Python IDE for Eclipse)
+*.pydevproject
+
+# CDT-specific (C/C++ Development Tooling)
+.cproject
+
+# CDT- autotools
+.autotools
+
+# Java annotation processor (APT)
+.factorypath
+
+# PDT-specific (PHP Development Tools)
+.buildpath
+
+# sbteclipse plugin
+.target
+
+# Tern plugin
+.tern-project
+
+# TeXlipse plugin
+.texlipse
+
+# STS (Spring Tool Suite)
+.springBeans
+
+# Code Recommenders
+.recommenders/
+
+# Annotation Processing
+.apt_generated/
+.apt_generated_test/
+
+# Scala IDE specific (Scala & Java development for Eclipse)
+.cache-main
+.scala_dependencies
+.worksheet
+
+# Uncomment this line if you wish to ignore the project description file.
+# Typically, this file would be tracked if it contains build/dependency configurations:
+#.project
+
+### Eclipse Patch ###
+# Spring Boot Tooling
+.sts4-cache/
+
+### Java ###
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+# End of https://www.toptal.com/developers/gitignore/api/java,eclipse
+
diff --git a/ProfCalculator/.classpath b/ProfCalculator/.classpath
index 2b1ff5c..3c48f73 100644
--- a/ProfCalculator/.classpath
+++ b/ProfCalculator/.classpath
@@ -1,11 +1,10 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-13">
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/java-11-openjdk">
 		<attributes>
 			<attribute name="module" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.jdt.USER_LIBRARY/JavaFx"/>
 	<classpathentry kind="con" path="org.eclipse.jdt.USER_LIBRARY/JavaFX"/>
 	<classpathentry kind="src" path="src"/>
 	<classpathentry kind="output" path="bin"/>
diff --git a/ProfCalculator/.settings/org.eclipse.jdt.core.prefs b/ProfCalculator/.settings/org.eclipse.jdt.core.prefs
index ef28d2b..cd8d089 100644
--- a/ProfCalculator/.settings/org.eclipse.jdt.core.prefs
+++ b/ProfCalculator/.settings/org.eclipse.jdt.core.prefs
@@ -1,8 +1,9 @@
 eclipse.preferences.version=1
 org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode=enabled
-org.eclipse.jdt.core.compiler.codegen.targetPlatform=13
+org.eclipse.jdt.core.compiler.codegen.methodParameters=do not generate
+org.eclipse.jdt.core.compiler.codegen.targetPlatform=11
 org.eclipse.jdt.core.compiler.codegen.unusedLocal=preserve
-org.eclipse.jdt.core.compiler.compliance=13
+org.eclipse.jdt.core.compiler.compliance=11
 org.eclipse.jdt.core.compiler.debug.lineNumber=generate
 org.eclipse.jdt.core.compiler.debug.localVariable=generate
 org.eclipse.jdt.core.compiler.debug.sourceFile=generate
@@ -10,5 +11,5 @@ org.eclipse.jdt.core.compiler.problem.assertIdentifier=error
 org.eclipse.jdt.core.compiler.problem.enablePreviewFeatures=disabled
 org.eclipse.jdt.core.compiler.problem.enumIdentifier=error
 org.eclipse.jdt.core.compiler.problem.reportPreviewFeatures=warning
-org.eclipse.jdt.core.compiler.release=enabled
-org.eclipse.jdt.core.compiler.source=13
+org.eclipse.jdt.core.compiler.release=disabled
+org.eclipse.jdt.core.compiler.source=11
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/ProfCalculator.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/ProfCalculator.java
index 8f7fb4f..d31428d 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/ProfCalculator.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/ProfCalculator.java
@@ -1,12 +1,13 @@
 package de.uulm.sp.swt.profcalculator;
 
 import de.uulm.sp.swt.profcalculator.expressions.Addition;
+import de.uulm.sp.swt.profcalculator.expressions.Div;
 import de.uulm.sp.swt.profcalculator.expressions.Expression;
 import de.uulm.sp.swt.profcalculator.expressions.Multiplication;
 import de.uulm.sp.swt.profcalculator.expressions.NecessaryBrackets;
+import de.uulm.sp.swt.profcalculator.expressions.Sub;
 import de.uulm.sp.swt.profcalculator.expressions.Value;
-import de.uulm.sp.swt.profcalculator.gui.BlueFontGUIFactory;
-import de.uulm.sp.swt.profcalculator.gui.GUIFactory;
+import de.uulm.sp.swt.profcalculator.gui.*;
 import javafx.application.Application;
 import javafx.event.ActionEvent;
 import javafx.event.EventHandler;
@@ -25,14 +26,16 @@ public class ProfCalculator	extends Application implements EventHandler<ActionEv
 
 	private Expression expression = DEFAULT_VALUE;
 	
-	private GUIFactory guiFactory = new BlueFontGUIFactory();
+	private GUIFactory guiFactory = new TerminalStyleFactory();
 
 	private Label errorLabel = guiFactory.createLabel();
 
-	private TextField inputField = new TextField();
+	private TextField inputField = guiFactory.createTextField();
 
 	private Button additionButton = guiFactory.createButton("+");
+	private Button subtractionButton = guiFactory.createButton("-");
 	private Button multiplicationButton = guiFactory.createButton("*");
+	private Button divisionButton = guiFactory.createButton("/");
 
 	private Label resultLabel = guiFactory.createLabel();
 
@@ -41,34 +44,43 @@ public void start(Stage stage) throws Exception {
 		stage.setTitle("Professorial Calculator");
 		errorLabel.setTextFill(Color.web("#AA0000"));
 
-		VBox layout = new VBox(10, errorLabel, inputField, additionButton, multiplicationButton, resultLabel);
+		VBox layout = new VBox(10, errorLabel, inputField, additionButton, subtractionButton, multiplicationButton, divisionButton, resultLabel);
 		layout.setPadding(new Insets(20, 80, 20, 80));
+		layout.setStyle(guiFactory.getBackgroundColorStyle());
 		Scene scene = new Scene(layout);
 
 		stage.setScene(scene);
 		stage.show();
 		additionButton.setOnAction(this);
+		subtractionButton.setOnAction(this);
 		multiplicationButton.setOnAction(this);
+		divisionButton.setOnAction(this);
+		
 		updateGUI();
 	}
 
 	@Override
 	public void handle(ActionEvent event) {
 		try {
-			int newValue = Integer.parseInt(inputField.getText());
+			double newValue = Double.parseDouble(inputField.getText());
 			if (event.getSource() == additionButton) {
 				expression = new Addition(expression, new Value(newValue));
 				Logger.getLogger().log("+ " + newValue);
-			}
-			else if (event.getSource() == multiplicationButton) {
+			} else if (event.getSource() == subtractionButton) {
+				expression = new Sub(expression, new Value(newValue));
+			} else if (event.getSource() == multiplicationButton) {
 				expression = new Multiplication(expression, new Value(newValue));
 				Logger.getLogger().log("* " + newValue);
+			} else if (event.getSource() == divisionButton) {
+				expression = new Div(expression, new Value(newValue));
 			}
 			expression = new NecessaryBrackets(expression);
 			updateGUI();
 			inputField.requestFocus();
 		} catch (NumberFormatException e) {
 			errorLabel.setText("\"" + inputField.getText() + "\" is not a valid integer");
+		}catch (ArithmeticException e) {
+			errorLabel.setText(e.getMessage());
 		}
 	}
 
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Addition.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Addition.java
index 290f903..fb3617c 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Addition.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Addition.java
@@ -14,7 +14,7 @@ public String toString(Expression parent) {
 		return left.toString(this) + " + " + right.toString(this);
 	}
 
-	public int evaluate() {
+	public double evaluate() {
 		return left.evaluate() + right.evaluate();
 	}
 	
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Div.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Div.java
new file mode 100644
index 0000000..27422af
--- /dev/null
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Div.java
@@ -0,0 +1,23 @@
+package de.uulm.sp.swt.profcalculator.expressions;
+
+public class Div extends Expression {
+
+	public Expression left;
+	public Expression right;
+
+	public Div(Expression left, Expression right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	public String toString(Expression parent) {
+		return left.toString(this) + " / " + right.toString(this);
+	}
+
+	public double evaluate() {
+		if (right.evaluate() == 0)
+			throw new ArithmeticException("Division by zero is not allowed!");
+		return left.evaluate() / right.evaluate();
+	}
+	
+}
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Expression.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Expression.java
index 2047d49..2796a81 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Expression.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Expression.java
@@ -2,7 +2,7 @@
 
 public abstract class Expression {
 
-	public abstract int evaluate();
+	public abstract double evaluate();
 
 	public abstract String toString(Expression parent);
 
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Multiplication.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Multiplication.java
index 7256be3..f48d144 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Multiplication.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Multiplication.java
@@ -14,7 +14,7 @@ public String toString(Expression parent) {
 		return left.toString(this) + " * " + right.toString(this);
 	}
 
-	public int evaluate() {
+	public double evaluate() {
 		return left.evaluate() * right.evaluate();
 	}
 	
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/NecessaryBrackets.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/NecessaryBrackets.java
index 177b051..35963ec 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/NecessaryBrackets.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/NecessaryBrackets.java
@@ -11,14 +11,15 @@ public NecessaryBrackets(Expression expression) {
 	@Override
 	public String toString(Expression parent) {
 		String childString = expression.toString(parent);
-		if (parent instanceof Multiplication && expression instanceof Addition) {
+		if ((parent instanceof Multiplication && (expression instanceof Addition || expression instanceof Sub)) ||
+			(parent instanceof Div && (expression instanceof Addition || expression instanceof Sub))) {
 			childString = "(" + childString + ")";
 		}
 		return childString;
 	}
 
 	@Override
-	public int evaluate() {
+	public double evaluate() {
 		return expression.evaluate();
 	}
 
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Sub.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Sub.java
new file mode 100644
index 0000000..403934c
--- /dev/null
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Sub.java
@@ -0,0 +1,21 @@
+package de.uulm.sp.swt.profcalculator.expressions;
+
+public class Sub extends Expression {
+	
+	public Expression left;
+	public Expression right;
+
+	public Sub(Expression left, Expression right) {
+		this.left = left;
+		this.right = right;
+	}
+
+	public String toString(Expression parent) {
+		return left.toString(this) + " - " + right.toString(this);
+	}
+
+	public double evaluate() {
+		return left.evaluate() - right.evaluate();
+	}
+	
+}
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Value.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Value.java
index c9f9ed6..b5e2332 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Value.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/expressions/Value.java
@@ -2,9 +2,9 @@
 
 public class Value extends Expression {
 
-	Integer value;
+	Double value;
 
-	public Value(int value) {
+	public Value(double value) {
 		this.value = value;
 	}
 
@@ -13,8 +13,8 @@ public String toString(Expression parent) {
 	}
 
 	@Override
-	public int evaluate() {
-		return value.intValue();
+	public double evaluate() {
+		return value;
 	}
 
 }
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/BlueFontGUIFactory.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/BlueFontGUIFactory.java
index 2895784..1108fd0 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/BlueFontGUIFactory.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/BlueFontGUIFactory.java
@@ -2,13 +2,15 @@
 
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
+import javafx.scene.control.TextField;
 import javafx.scene.paint.Color;
-import javafx.scene.text.Font;
 
 public class BlueFontGUIFactory implements GUIFactory {
 	
 	final static Color BLUE = Color.web("#0000AA");
 	
+	public final static String BLUE_HEX_CODE = "#0000aa";
+	
 	@Override
 	public Label createLabel() {
 		Label label = new Label();
@@ -23,4 +25,17 @@ public Button createButton(String title) {
 		return button;
 	}
 
+	@Override
+	public TextField createTextField() {
+		TextField textField = new TextField();
+		textField.setStyle("-fx-text-fill: " + BLUE_HEX_CODE + ";");
+		return textField;
+	}
+
+	@Override
+	public String getBackgroundColorStyle() {
+		//this way the default values are used
+		return null;
+	}
+
 }
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/GUIFactory.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/GUIFactory.java
index 146d358..db44a15 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/GUIFactory.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/GUIFactory.java
@@ -2,6 +2,7 @@
 
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
+import javafx.scene.control.TextField;
 
 public interface GUIFactory {
 
@@ -9,4 +10,8 @@ public interface GUIFactory {
 
 	Button createButton(String title);
 
+	TextField createTextField();
+	
+	String getBackgroundColorStyle();
+
 }
\ No newline at end of file
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/LargeFontGUIFactory.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/LargeFontGUIFactory.java
index f482bb3..67f1e77 100644
--- a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/LargeFontGUIFactory.java
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/LargeFontGUIFactory.java
@@ -2,6 +2,7 @@
 
 import javafx.scene.control.Button;
 import javafx.scene.control.Label;
+import javafx.scene.control.TextField;
 import javafx.scene.text.Font;
 
 public class LargeFontGUIFactory implements GUIFactory {
@@ -22,4 +23,17 @@ public Button createButton(String title) {
 		return button;
 	}
 
+	@Override
+	public TextField createTextField() {
+		TextField textField = new TextField();
+		textField.setFont(FONT);
+		return textField;
+	}
+
+	@Override
+	public String getBackgroundColorStyle() {
+		//this way the default values are used
+		return null;
+	}
+
 }
diff --git a/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/TerminalStyleFactory.java b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/TerminalStyleFactory.java
new file mode 100644
index 0000000..b6ca3a5
--- /dev/null
+++ b/ProfCalculator/src/de/uulm/sp/swt/profcalculator/gui/TerminalStyleFactory.java
@@ -0,0 +1,55 @@
+package de.uulm.sp.swt.profcalculator.gui;
+
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.control.TextField;
+import javafx.scene.paint.Color;
+
+public class TerminalStyleFactory implements GUIFactory {
+	
+	
+	final static String BORDER_WIDTH = "2px";
+
+	final static Color LIME = Color.LIME;
+	final static Color BLACK = Color.BLACK;
+	final static Color WHITE = Color.WHITE;
+	final static Color GREY = Color.GREY;
+	
+	public final static String WHITE_HEX_CODE = "#ffffff";
+	public final static String BLACK_HEX_CODE = "#000000";
+	public final static String GREY_HEX_CODE = "#808080";
+	public final static String LIME_HEX_CODE = "#00ff00";
+	
+	private final static String BACKGROUND_COLOR_STYLE = "-fx-background-color: " + BLACK_HEX_CODE + ";";
+	
+	final static int CORNER_RADIUS = 5;
+
+	@Override
+	public Label createLabel() {
+		Label label = new Label();
+		label.setTextFill(LIME);
+		return label;
+	}
+
+	@Override
+	public Button createButton(String title) {
+		Button button = new Button(title);
+		button.setTextFill(LIME);
+		button.setStyle("-fx-border-color: " + WHITE_HEX_CODE + "; -fx-border-width: " + BORDER_WIDTH + "; -fx-background-color: " + BLACK_HEX_CODE + "; -fx-border-radius: "+CORNER_RADIUS+"; -fx-background-radius: "+CORNER_RADIUS+";");
+		return button;
+	}
+
+	@Override
+	public TextField createTextField() {
+		TextField textField = new TextField();
+		System.out.println(LIME.toString());
+		textField.setStyle("-fx-background-color: " + GREY_HEX_CODE + "; -fx-text-fill: " + LIME_HEX_CODE + ";");
+		return textField;
+	}
+
+	@Override
+	public String getBackgroundColorStyle() {
+		return BACKGROUND_COLOR_STYLE;
+	}
+
+}