diff --git a/.gitignore b/.gitignore
index 1b6985c..e66edb7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,45 @@
-# Ignore Gradle project-specific cache directory
+.vscode
 .gradle
+**/build/
+!src/**/build/
 
-# Ignore Gradle build output directory
-build
+**/bin
+
+# Ignore Gradle GUI config
+gradle-app.setting
+
+# Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
+!gradle-wrapper.jar
+
+# Avoid ignore Gradle wrappper properties
+!gradle-wrapper.properties
+
+# Cache of project
+.gradletasknamecache
+
+# Eclipse Gradle plugin generated files
+# Eclipse Core
+.project
+# JDT-specific (Eclipse Java Development Tools)
+.classpath
+
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# 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*
+replay_pid*
+
+*.minisig
diff --git a/app/src/main/java/expr/Add.java b/app/src/main/java/expr/Add.java
new file mode 100644
index 0000000..ec8e6fb
--- /dev/null
+++ b/app/src/main/java/expr/Add.java
@@ -0,0 +1,18 @@
+package expr;
+
+class Add extends BinaryExpr {
+
+    Add(Expr expr1, Expr expr2) {
+        super(expr1, expr2);
+        precedence1 = 0;
+        precedence2 = 0;
+    }
+
+    public double op(double op1, double op2) {
+        return op1 + op2;
+    }
+
+    protected String opString() {
+        return "+";
+    }
+}
diff --git a/app/src/main/java/expr/BinaryExpr.java b/app/src/main/java/expr/BinaryExpr.java
new file mode 100644
index 0000000..49cb462
--- /dev/null
+++ b/app/src/main/java/expr/BinaryExpr.java
@@ -0,0 +1,37 @@
+package expr;
+
+abstract class BinaryExpr extends Expr {
+
+    private Expr expr1;
+    private Expr expr2;
+    protected int precedence1;
+    protected int precedence2;
+
+    protected BinaryExpr(Expr expr1, Expr expr2) {
+        this.expr1 = expr1;
+        this.expr2 = expr2;
+    }
+
+    protected abstract double op(double op1, double op2);
+
+    protected abstract String opString();
+
+    public String toString(int prec) {
+        StringBuilder builder = new StringBuilder();
+        boolean parentheses = prec > precedence1;
+        if (parentheses) {
+            builder.append('(');
+        }
+        builder.append(expr1.toString(precedence1));
+        builder.append(opString());
+        builder.append(expr2.toString(precedence2));
+        if (parentheses) {
+            builder.append(')');
+        }
+        return builder.toString();
+    }
+
+    public double value(Environment env) {
+        return op(expr1.value(env), expr2.value(env));
+    }
+}
diff --git a/app/src/main/java/expr/Div.java b/app/src/main/java/expr/Div.java
new file mode 100644
index 0000000..b27ef43
--- /dev/null
+++ b/app/src/main/java/expr/Div.java
@@ -0,0 +1,21 @@
+package expr;
+
+import util.XLException;
+
+class Div extends BinaryExpr {
+
+    Div(Expr expr1, Expr expr2) {
+        super(expr1, expr2);
+        precedence1 = 1;
+        precedence2 = 2;
+    }
+
+    public double op(double op1, double op2) {
+        if (op2 != 0) return op1 / op2;
+        else throw new XLException("division by zero");
+    }
+
+    protected String opString() {
+        return "/";
+    }
+}
diff --git a/app/src/main/java/expr/Environment.java b/app/src/main/java/expr/Environment.java
new file mode 100644
index 0000000..eab570c
--- /dev/null
+++ b/app/src/main/java/expr/Environment.java
@@ -0,0 +1,6 @@
+package expr;
+
+public interface Environment {
+
+    public double value(String name);
+}
diff --git a/app/src/main/java/expr/Expr.java b/app/src/main/java/expr/Expr.java
new file mode 100644
index 0000000..81499f5
--- /dev/null
+++ b/app/src/main/java/expr/Expr.java
@@ -0,0 +1,38 @@
+package expr;
+
+/**
+ * An <code>Expr</code> object represents a real valued expression that may contain variables. The
+ * value of a variable is obtained from an <code>Environment</code> object by specifying the name of
+ * the variable.
+ *
+ * @see Environment
+ * @author Lennart Andersson
+ */
+public abstract class Expr {
+
+    /**
+     * The <code>toString</code> method returns a <code>String</code> representation of this
+     * expression without unnecessary parentheses.
+     *
+     * @return the <code>String</code> representation of this expression.
+     */
+    public String toString() {
+        return toString(0);
+    }
+
+    /*
+     * toString(prec) returns a string representation of this expression without
+     * unnecessary parentheses. The prec argument specifies the precedence level
+     * enclosing expression and is used to control the precedence of
+     * parentheses.
+     */
+    public abstract String toString(int prec);
+
+    /**
+     * The <code>value</code> method returns the value of this expression.
+     *
+     * @param env is the <code>Environment</code> containing the values of variables.
+     * @return the <code>double</code> value of this expression.
+     */
+    public abstract double value(Environment env);
+}
diff --git a/app/src/main/java/expr/ExprParser.java b/app/src/main/java/expr/ExprParser.java
new file mode 100644
index 0000000..a933265
--- /dev/null
+++ b/app/src/main/java/expr/ExprParser.java
@@ -0,0 +1,136 @@
+package expr;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StreamTokenizer;
+import java.io.StringReader;
+import java.util.regex.Pattern;
+import util.XLException;
+
+/**
+ * An <code>ExprParser</code> object is a parser provides a factory method for building <code>Expr
+ * </code> objects from text representations of arithmetic expressions. The text containing the
+ * expression should adhere to the following grammar.
+ *
+ * <pre>
+ *
+ *
+ *
+ *    expr ::= term {addop term}
+ *    term ::= factor {mulop factor}
+ *    factor ::= number | variable | &quot;(&quot; expr &quot;)&quot;
+ *    addop ::= &quot;+&quot; | &quot;-&quot;
+ *    mulop ::= &quot;*&quot; | &quot;/&quot;
+ *
+ *
+ *
+ * </pre>
+ *
+ * where <code>number</code> is an unsigned number according to <code>StreamTokenizer</code> and
+ * <code>variable</code> is a string of letters and digits. The first character must be a letter.
+ *
+ * @see Expr
+ * @see StreamTokenizer
+ * @author Lennart Andersson
+ */
+public class ExprParser {
+
+    private int token;
+    private StreamTokenizer tokenizer;
+
+    /**
+     * The <code>build</code> method returns an <code>Expr</code> representation of the expression
+     * provided by <code>reader</code>.
+     *
+     * @param reader a <code>Reader</code> provided the string to be parsed.
+     * @return an <code>Expr</code> representation of the string.
+     * @exception IOException if the <code>reader</code> does not deliver data.
+     * @exception ExprParserException if the reader input violates the grammar.
+     */
+    public Expr build(Reader reader) throws IOException {
+        tokenizer = new StreamTokenizer(reader);
+        tokenizer.ordinaryChar('-');
+        tokenizer.ordinaryChar('/');
+        token = tokenizer.nextToken();
+        Expr e = expr();
+        if (token == StreamTokenizer.TT_EOF) return e;
+        else throw new XLException("trailing garbage");
+    }
+
+    /**
+     * The <code>build</code> method returns an <code>Expr</code> representation of the expression
+     * provided by the <code>input</code> string.
+     *
+     * @param input the <code>String</code> to be parsed.
+     * @return an <code>Expr</code> representation of the string.
+     * @exception IOException if the <code>input</code> does not deliver data.
+     * @exception XLException if the input violates the grammar.
+     */
+    public Expr build(String input) throws IOException {
+        return build(new StringReader(input));
+    }
+
+    private Expr expr() throws IOException {
+        Expr result, term;
+        result = term();
+        while (token == '+' || token == '-') {
+            int op = token;
+            token = tokenizer.nextToken();
+            term = term();
+            switch (op) {
+                case '+':
+                    result = new Add(result, term);
+                    break;
+                case '-':
+                    result = new Sub(result, term);
+                    break;
+            }
+        }
+        return result;
+    }
+
+    private Expr factor() throws IOException {
+        Expr e;
+        switch (token) {
+            case '(':
+                token = tokenizer.nextToken();
+                e = expr();
+                if (token != ')') throw new XLException("expecting \")\", found: " + token);
+                token = tokenizer.nextToken();
+                return e;
+            case StreamTokenizer.TT_NUMBER:
+                double x = tokenizer.nval;
+                token = tokenizer.nextToken();
+                return new Num(x);
+            case StreamTokenizer.TT_WORD:
+                String address = tokenizer.sval.toUpperCase();
+                if (!Pattern.matches("[A-Z][0-9]+", address))
+                    throw new XLException("illegal address: " + address);
+                token = tokenizer.nextToken();
+                return new Variable(address);
+            case StreamTokenizer.TT_EOF:
+                throw new XLException("unexpected end of text");
+            default:
+                throw new XLException("unexpected " + (char) token);
+        }
+    }
+
+    private Expr term() throws IOException {
+        Expr result, factor;
+        result = factor();
+        while (token == '*' || token == '/') {
+            int op = token;
+            token = tokenizer.nextToken();
+            factor = factor();
+            switch (op) {
+                case '*':
+                    result = new Mul(result, factor);
+                    break;
+                case '/':
+                    result = new Div(result, factor);
+                    break;
+            }
+        }
+        return result;
+    }
+}
diff --git a/app/src/main/java/expr/Mul.java b/app/src/main/java/expr/Mul.java
new file mode 100644
index 0000000..b5e2f24
--- /dev/null
+++ b/app/src/main/java/expr/Mul.java
@@ -0,0 +1,18 @@
+package expr;
+
+class Mul extends BinaryExpr {
+
+    Mul(Expr expr1, Expr expr2) {
+        super(expr1, expr2);
+        precedence1 = 1;
+        precedence2 = 1;
+    }
+
+    public double op(double op1, double op2) {
+        return op1 * op2;
+    }
+
+    protected String opString() {
+        return "*";
+    }
+}
diff --git a/app/src/main/java/expr/Num.java b/app/src/main/java/expr/Num.java
new file mode 100644
index 0000000..e724043
--- /dev/null
+++ b/app/src/main/java/expr/Num.java
@@ -0,0 +1,21 @@
+package expr;
+
+import util.NumberAdjustment;
+
+class Num extends Expr {
+
+    private static NumberAdjustment adjustment = new NumberAdjustment(0, 2);
+    private double value;
+
+    Num(double value) {
+        this.value = value;
+    }
+
+    public String toString(int prec) {
+        return adjustment.right(value);
+    }
+
+    public double value(Environment env) {
+        return value;
+    }
+}
diff --git a/app/src/main/java/expr/Sub.java b/app/src/main/java/expr/Sub.java
new file mode 100644
index 0000000..80d8141
--- /dev/null
+++ b/app/src/main/java/expr/Sub.java
@@ -0,0 +1,18 @@
+package expr;
+
+class Sub extends BinaryExpr {
+
+    Sub(Expr expr1, Expr expr2) {
+        super(expr1, expr2);
+        precedence1 = 0;
+        precedence2 = 1;
+    }
+
+    public double op(double op1, double op2) {
+        return op1 - op2;
+    }
+
+    protected String opString() {
+        return "-";
+    }
+}
diff --git a/app/src/main/java/expr/TestExpr.java b/app/src/main/java/expr/TestExpr.java
new file mode 100644
index 0000000..62765a3
--- /dev/null
+++ b/app/src/main/java/expr/TestExpr.java
@@ -0,0 +1,30 @@
+package expr;
+
+import java.io.IOException;
+
+public class TestExpr {
+
+    public static void main(String[] args) {
+        ExprParser parser = new ExprParser();
+        try {
+            Expr expr = parser.build("1+2*3");
+            System.out.println(expr);
+            System.out.println(expr.value(null));
+            expr = parser.build("A3+A2*A1");
+            Environment env =
+                    new Environment() {
+                        public double value(String name) {
+                            if (name.equals("A3")) return 1;
+                            if (name.equals("A2")) return 2;
+                            if (name.equals("A1")) return 3;
+                            System.out.println(name + " is undefined");
+                            return 0;
+                        }
+                    };
+            System.out.println(expr);
+            System.out.println(expr.value(env));
+        } catch (IOException e) {
+            System.err.println(e.getMessage());
+        }
+    }
+}
diff --git a/app/src/main/java/expr/Variable.java b/app/src/main/java/expr/Variable.java
new file mode 100644
index 0000000..f96075e
--- /dev/null
+++ b/app/src/main/java/expr/Variable.java
@@ -0,0 +1,18 @@
+package expr;
+
+class Variable extends Expr {
+
+    private String name;
+
+    Variable(String name) {
+        this.name = name;
+    }
+
+    public String toString(int prec) {
+        return name.toString();
+    }
+
+    public double value(Environment env) {
+        return env.value(name);
+    }
+}
diff --git a/app/src/main/java/gui/BorderPanel.java b/app/src/main/java/gui/BorderPanel.java
new file mode 100644
index 0000000..85c62e0
--- /dev/null
+++ b/app/src/main/java/gui/BorderPanel.java
@@ -0,0 +1,13 @@
+package gui;
+
+import java.awt.BorderLayout;
+import java.awt.Color;
+import javax.swing.JPanel;
+
+public class BorderPanel extends JPanel {
+
+    protected BorderPanel() {
+        super(new BorderLayout(2, 2));
+        setBackground(Color.BLACK);
+    }
+}
diff --git a/app/src/main/java/gui/ColoredLabel.java b/app/src/main/java/gui/ColoredLabel.java
new file mode 100644
index 0000000..128f63a
--- /dev/null
+++ b/app/src/main/java/gui/ColoredLabel.java
@@ -0,0 +1,22 @@
+package gui;
+
+import java.awt.Color;
+import javax.swing.JLabel;
+import javax.swing.SwingConstants;
+
+public class ColoredLabel extends JLabel {
+
+    public ColoredLabel(String text) {
+        this(text, Color.WHITE, SwingConstants.LEFT);
+    }
+
+    public ColoredLabel(String text, Color color) {
+        this(text, color, SwingConstants.LEFT);
+    }
+
+    public ColoredLabel(String text, Color color, int alignment) {
+        super(text, alignment);
+        setBackground(color);
+        setOpaque(true);
+    }
+}
diff --git a/app/src/main/java/gui/CurrentLabel.java b/app/src/main/java/gui/CurrentLabel.java
new file mode 100644
index 0000000..525a488
--- /dev/null
+++ b/app/src/main/java/gui/CurrentLabel.java
@@ -0,0 +1,10 @@
+package gui;
+
+import java.awt.Color;
+
+public class CurrentLabel extends ColoredLabel {
+
+    public CurrentLabel() {
+        super("A1", Color.WHITE);
+    }
+}
diff --git a/app/src/main/java/gui/Editor.java b/app/src/main/java/gui/Editor.java
new file mode 100644
index 0000000..ae7b4d8
--- /dev/null
+++ b/app/src/main/java/gui/Editor.java
@@ -0,0 +1,11 @@
+package gui;
+
+import java.awt.Color;
+import javax.swing.JTextField;
+
+public class Editor extends JTextField {
+
+    public Editor() {
+        setBackground(Color.WHITE);
+    }
+}
diff --git a/app/src/main/java/gui/GridPanel.java b/app/src/main/java/gui/GridPanel.java
new file mode 100644
index 0000000..b70ab60
--- /dev/null
+++ b/app/src/main/java/gui/GridPanel.java
@@ -0,0 +1,13 @@
+package gui;
+
+import java.awt.Color;
+import java.awt.GridLayout;
+import javax.swing.JPanel;
+
+public class GridPanel extends JPanel {
+
+    public GridPanel(int rows, int columns) {
+        super(new GridLayout(rows, columns, 2, 2));
+        setBackground(Color.BLACK);
+    }
+}
diff --git a/app/src/main/java/gui/RowLabels.java b/app/src/main/java/gui/RowLabels.java
new file mode 100644
index 0000000..82a4b15
--- /dev/null
+++ b/app/src/main/java/gui/RowLabels.java
@@ -0,0 +1,15 @@
+package gui;
+
+import static java.awt.Color.LIGHT_GRAY;
+import static javax.swing.SwingConstants.RIGHT;
+
+class RowLabels extends GridPanel {
+
+    RowLabels(int rows) {
+        super(rows + 1, 1);
+        add(new ColoredLabel("", LIGHT_GRAY, RIGHT));
+        for (int i = 1; i <= rows; i++) {
+            add(new ColoredLabel(String.valueOf(i), LIGHT_GRAY, RIGHT));
+        }
+    }
+}
diff --git a/app/src/main/java/gui/SheetPanel.java b/app/src/main/java/gui/SheetPanel.java
new file mode 100644
index 0000000..4f777e8
--- /dev/null
+++ b/app/src/main/java/gui/SheetPanel.java
@@ -0,0 +1,12 @@
+package gui;
+
+import static java.awt.BorderLayout.CENTER;
+import static java.awt.BorderLayout.WEST;
+
+public class SheetPanel extends BorderPanel {
+
+    public SheetPanel(int rows, int columns) {
+        add(WEST, new RowLabels(rows));
+        add(CENTER, new SlotLabels(rows, columns));
+    }
+}
diff --git a/app/src/main/java/gui/SlotLabel.java b/app/src/main/java/gui/SlotLabel.java
new file mode 100644
index 0000000..5f26e9b
--- /dev/null
+++ b/app/src/main/java/gui/SlotLabel.java
@@ -0,0 +1,10 @@
+package gui;
+
+import java.awt.Color;
+
+public class SlotLabel extends ColoredLabel {
+
+    public SlotLabel() {
+        super("                    ", Color.WHITE, RIGHT);
+    }
+}
diff --git a/app/src/main/java/gui/SlotLabels.java b/app/src/main/java/gui/SlotLabels.java
new file mode 100644
index 0000000..2423216
--- /dev/null
+++ b/app/src/main/java/gui/SlotLabels.java
@@ -0,0 +1,28 @@
+package gui;
+
+import java.awt.Color;
+import java.util.ArrayList;
+import java.util.List;
+import javax.swing.SwingConstants;
+
+public class SlotLabels extends GridPanel {
+
+    private List<SlotLabel> labelList;
+
+    public SlotLabels(int rows, int cols) {
+        super(rows + 1, cols);
+        labelList = new ArrayList<SlotLabel>(rows * cols);
+        for (char ch = 'A'; ch < 'A' + cols; ch++) {
+            add(new ColoredLabel(Character.toString(ch), Color.LIGHT_GRAY, SwingConstants.CENTER));
+        }
+        for (int row = 1; row <= rows; row++) {
+            for (char ch = 'A'; ch < 'A' + cols; ch++) {
+                SlotLabel label = new SlotLabel();
+                add(label);
+                labelList.add(label);
+            }
+        }
+        SlotLabel firstLabel = labelList.get(0);
+        firstLabel.setBackground(Color.YELLOW);
+    }
+}
diff --git a/app/src/main/java/gui/StatusLabel.java b/app/src/main/java/gui/StatusLabel.java
new file mode 100644
index 0000000..c902879
--- /dev/null
+++ b/app/src/main/java/gui/StatusLabel.java
@@ -0,0 +1,16 @@
+package gui;
+
+import java.awt.Color;
+import java.util.Observable;
+import java.util.Observer;
+
+public class StatusLabel extends ColoredLabel implements Observer {
+
+    public StatusLabel() {
+        super("", Color.WHITE);
+    }
+
+    public void update(Observable observable, Object object) {
+        setText("");
+    }
+}
diff --git a/app/src/main/java/gui/StatusPanel.java b/app/src/main/java/gui/StatusPanel.java
new file mode 100644
index 0000000..2c31617
--- /dev/null
+++ b/app/src/main/java/gui/StatusPanel.java
@@ -0,0 +1,12 @@
+package gui;
+
+import static java.awt.BorderLayout.CENTER;
+import static java.awt.BorderLayout.WEST;
+
+public class StatusPanel extends BorderPanel {
+
+    protected StatusPanel(StatusLabel statusLabel) {
+        add(WEST, new CurrentLabel());
+        add(CENTER, statusLabel);
+    }
+}
diff --git a/app/src/main/java/gui/XL.java b/app/src/main/java/gui/XL.java
new file mode 100644
index 0000000..6dc9079
--- /dev/null
+++ b/app/src/main/java/gui/XL.java
@@ -0,0 +1,49 @@
+package gui;
+
+import static java.awt.BorderLayout.CENTER;
+import static java.awt.BorderLayout.NORTH;
+import static java.awt.BorderLayout.SOUTH;
+
+import javax.swing.JFrame;
+import javax.swing.JPanel;
+import gui.menu.XLMenuBar;
+
+public class XL extends JFrame {
+
+    private static final int ROWS = 10, COLUMNS = 8;
+    private XLCounter counter;
+    private StatusLabel statusLabel = new StatusLabel();
+    private XLList xlList;
+
+    public XL(XL oldXL) {
+        this(oldXL.xlList, oldXL.counter);
+    }
+
+    public XL(XLList xlList, XLCounter counter) {
+        super("Untitled-" + counter);
+        this.xlList = xlList;
+        this.counter = counter;
+        xlList.add(this);
+        counter.increment();
+        JPanel statusPanel = new StatusPanel(statusLabel);
+        JPanel sheetPanel = new SheetPanel(ROWS, COLUMNS);
+        Editor editor = new Editor();
+        add(NORTH, statusPanel);
+        add(CENTER, editor);
+        add(SOUTH, sheetPanel);
+        setJMenuBar(new XLMenuBar(this, xlList, statusLabel));
+        pack();
+        setDefaultCloseOperation(EXIT_ON_CLOSE);
+        setResizable(false);
+        setVisible(true);
+    }
+
+    public void rename(String title) {
+        setTitle(title);
+        xlList.setChanged();
+    }
+
+    public static void main(String[] args) {
+        new XL(new XLList(), new XLCounter());
+    }
+}
diff --git a/app/src/main/java/gui/XLCounter.java b/app/src/main/java/gui/XLCounter.java
new file mode 100644
index 0000000..7bf609a
--- /dev/null
+++ b/app/src/main/java/gui/XLCounter.java
@@ -0,0 +1,14 @@
+package gui;
+
+public class XLCounter {
+
+    private int counter;
+
+    public void increment() {
+        counter++;
+    }
+
+    public String toString() {
+        return Integer.toString(counter);
+    }
+}
diff --git a/app/src/main/java/gui/XLList.java b/app/src/main/java/gui/XLList.java
new file mode 100644
index 0000000..7a937ef
--- /dev/null
+++ b/app/src/main/java/gui/XLList.java
@@ -0,0 +1,40 @@
+package gui;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Observable;
+
+public class XLList extends Observable implements Iterable<XL> {
+
+    private List<XL> list = new ArrayList<XL>();
+
+    public void add(XL xl) {
+        list.add(xl);
+        setChanged();
+        notifyObservers();
+    }
+
+    public boolean isEmpty() {
+        return list.isEmpty();
+    }
+
+    public Iterator<XL> iterator() {
+        return list.iterator();
+    }
+
+    public XL last() {
+        return list.get(list.size() - 1);
+    }
+
+    public void remove(XL xl) {
+        list.remove(xl);
+        setChanged();
+        notifyObservers();
+    }
+
+    public void setChanged() {
+        super.setChanged();
+        notifyObservers();
+    }
+}
diff --git a/app/src/main/java/gui/menu/ClearAllMenuItem.java b/app/src/main/java/gui/menu/ClearAllMenuItem.java
new file mode 100644
index 0000000..ca9a04c
--- /dev/null
+++ b/app/src/main/java/gui/menu/ClearAllMenuItem.java
@@ -0,0 +1,17 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JMenuItem;
+
+class ClearAllMenuItem extends JMenuItem implements ActionListener {
+
+    public ClearAllMenuItem() {
+        super("Clear all");
+        addActionListener(this);
+    }
+
+    public void actionPerformed(ActionEvent e) {
+        // TODO
+    }
+}
diff --git a/app/src/main/java/gui/menu/ClearMenuItem.java b/app/src/main/java/gui/menu/ClearMenuItem.java
new file mode 100644
index 0000000..f3e85a8
--- /dev/null
+++ b/app/src/main/java/gui/menu/ClearMenuItem.java
@@ -0,0 +1,17 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JMenuItem;
+
+class ClearMenuItem extends JMenuItem implements ActionListener {
+
+    public ClearMenuItem() {
+        super("Clear");
+        addActionListener(this);
+    }
+
+    public void actionPerformed(ActionEvent e) {
+        // TODO
+    }
+}
diff --git a/app/src/main/java/gui/menu/CloseMenuItem.java b/app/src/main/java/gui/menu/CloseMenuItem.java
new file mode 100644
index 0000000..ebb1225
--- /dev/null
+++ b/app/src/main/java/gui/menu/CloseMenuItem.java
@@ -0,0 +1,30 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JMenuItem;
+import gui.XL;
+import gui.XLList;
+
+class CloseMenuItem extends JMenuItem implements ActionListener {
+
+    private XL xl;
+    private XLList xlList;
+
+    public CloseMenuItem(XL xl, XLList xlList) {
+        super("Close");
+        this.xl = xl;
+        this.xlList = xlList;
+        addActionListener(this);
+    }
+
+    public void actionPerformed(ActionEvent event) {
+        xlList.remove(xl);
+        xl.dispose();
+        if (xlList.isEmpty()) {
+            System.exit(0);
+        } else {
+            xlList.last().toFront();
+        }
+    }
+}
diff --git a/app/src/main/java/gui/menu/LoadMenuItem.java b/app/src/main/java/gui/menu/LoadMenuItem.java
new file mode 100644
index 0000000..a8ccfb3
--- /dev/null
+++ b/app/src/main/java/gui/menu/LoadMenuItem.java
@@ -0,0 +1,21 @@
+package gui.menu;
+
+import java.io.FileNotFoundException;
+import javax.swing.JFileChooser;
+import gui.StatusLabel;
+import gui.XL;
+
+class LoadMenuItem extends OpenMenuItem {
+
+    public LoadMenuItem(XL xl, StatusLabel statusLabel) {
+        super(xl, statusLabel, "Load");
+    }
+
+    protected void action(String path) throws FileNotFoundException {
+        // TODO
+    }
+
+    protected int openDialog(JFileChooser fileChooser) {
+        return fileChooser.showOpenDialog(xl);
+    }
+}
diff --git a/app/src/main/java/gui/menu/NewMenuItem.java b/app/src/main/java/gui/menu/NewMenuItem.java
new file mode 100644
index 0000000..c5cc4cc
--- /dev/null
+++ b/app/src/main/java/gui/menu/NewMenuItem.java
@@ -0,0 +1,21 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JMenuItem;
+import gui.XL;
+
+class NewMenuItem extends JMenuItem implements ActionListener {
+
+    private XL xl;
+
+    public NewMenuItem(XL xl) {
+        super("New");
+        this.xl = xl;
+        addActionListener(this);
+    }
+
+    public void actionPerformed(ActionEvent event) {
+        new XL(xl);
+    }
+}
diff --git a/app/src/main/java/gui/menu/OpenMenuItem.java b/app/src/main/java/gui/menu/OpenMenuItem.java
new file mode 100644
index 0000000..a3c14a5
--- /dev/null
+++ b/app/src/main/java/gui/menu/OpenMenuItem.java
@@ -0,0 +1,45 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.io.File;
+import java.io.FileNotFoundException;
+import javax.swing.JFileChooser;
+import javax.swing.JMenuItem;
+import javax.swing.filechooser.FileFilter;
+import javax.swing.filechooser.FileNameExtensionFilter;
+import gui.StatusLabel;
+import gui.XL;
+
+public abstract class OpenMenuItem extends JMenuItem implements ActionListener {
+
+    protected StatusLabel statusLabel;
+    protected XL xl;
+
+    protected OpenMenuItem(XL xl, StatusLabel statusLabel, String title) {
+        super(title);
+        this.xl = xl;
+        this.statusLabel = statusLabel;
+        addActionListener(this);
+    }
+
+    protected abstract void action(String path) throws FileNotFoundException;
+
+    public void actionPerformed(ActionEvent event) {
+        JFileChooser fileChooser = new JFileChooser(".");
+        FileFilter filter = new FileNameExtensionFilter("XL files", "xl");
+        fileChooser.setFileFilter(filter);
+        int option = openDialog(fileChooser);
+        if (option == JFileChooser.APPROVE_OPTION) {
+            File file = fileChooser.getSelectedFile();
+            try {
+                action(file.toString());
+                xl.rename(file.getName());
+            } catch (FileNotFoundException e) {
+                statusLabel.setText(e.getMessage());
+            }
+        }
+    }
+
+    protected abstract int openDialog(JFileChooser fileChooser);
+}
diff --git a/app/src/main/java/gui/menu/SaveMenuItem.java b/app/src/main/java/gui/menu/SaveMenuItem.java
new file mode 100644
index 0000000..169a08e
--- /dev/null
+++ b/app/src/main/java/gui/menu/SaveMenuItem.java
@@ -0,0 +1,21 @@
+package gui.menu;
+
+import java.io.FileNotFoundException;
+import javax.swing.JFileChooser;
+import gui.StatusLabel;
+import gui.XL;
+
+class SaveMenuItem extends OpenMenuItem {
+
+    public SaveMenuItem(XL xl, StatusLabel statusLabel) {
+        super(xl, statusLabel, "Save");
+    }
+
+    protected void action(String path) throws FileNotFoundException {
+        // TODO
+    }
+
+    protected int openDialog(JFileChooser fileChooser) {
+        return fileChooser.showSaveDialog(xl);
+    }
+}
diff --git a/app/src/main/java/gui/menu/WindowMenu.java b/app/src/main/java/gui/menu/WindowMenu.java
new file mode 100644
index 0000000..2b8b375
--- /dev/null
+++ b/app/src/main/java/gui/menu/WindowMenu.java
@@ -0,0 +1,26 @@
+package gui.menu;
+
+import java.util.Observable;
+import java.util.Observer;
+import javax.swing.JMenu;
+import gui.XL;
+import gui.XLList;
+
+public class WindowMenu extends JMenu implements Observer {
+
+    private XLList xlList;
+
+    public WindowMenu(XLList xlList) {
+        super("Window");
+        this.xlList = xlList;
+        xlList.addObserver(this);
+        update(null, null);
+    }
+
+    public void update(Observable observable, Object object) {
+        removeAll();
+        for (XL xl : xlList) {
+            add(new WindowMenuItem(xl));
+        }
+    }
+}
diff --git a/app/src/main/java/gui/menu/WindowMenuItem.java b/app/src/main/java/gui/menu/WindowMenuItem.java
new file mode 100644
index 0000000..0ffd3d8
--- /dev/null
+++ b/app/src/main/java/gui/menu/WindowMenuItem.java
@@ -0,0 +1,21 @@
+package gui.menu;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import javax.swing.JMenuItem;
+import gui.XL;
+
+class WindowMenuItem extends JMenuItem implements ActionListener {
+
+    private XL xl;
+
+    public WindowMenuItem(XL xl) {
+        super(xl.getTitle());
+        this.xl = xl;
+        addActionListener(this);
+    }
+
+    public void actionPerformed(ActionEvent event) {
+        xl.toFront();
+    }
+}
diff --git a/app/src/main/java/gui/menu/XLMenuBar.java b/app/src/main/java/gui/menu/XLMenuBar.java
new file mode 100644
index 0000000..25bed14
--- /dev/null
+++ b/app/src/main/java/gui/menu/XLMenuBar.java
@@ -0,0 +1,24 @@
+package gui.menu;
+
+import javax.swing.JMenu;
+import javax.swing.JMenuBar;
+import gui.StatusLabel;
+import gui.XL;
+import gui.XLList;
+
+public class XLMenuBar extends JMenuBar {
+
+    public XLMenuBar(XL xl, XLList xlList, StatusLabel statusLabel) {
+        JMenu file = new JMenu("File");
+        JMenu edit = new JMenu("Edit");
+        file.add(new SaveMenuItem(xl, statusLabel));
+        file.add(new LoadMenuItem(xl, statusLabel));
+        file.add(new NewMenuItem(xl));
+        file.add(new CloseMenuItem(xl, xlList));
+        edit.add(new ClearMenuItem());
+        edit.add(new ClearAllMenuItem());
+        add(file);
+        add(edit);
+        add(new WindowMenu(xlList));
+    }
+}
diff --git a/app/src/main/java/util/Adjustment.java b/app/src/main/java/util/Adjustment.java
new file mode 100644
index 0000000..96b06f0
--- /dev/null
+++ b/app/src/main/java/util/Adjustment.java
@@ -0,0 +1,134 @@
+package util;
+
+/**
+ * Adjustment.java Created: Tue Oct 24 2005
+ *
+ * @author Lennart Andersson
+ * @version 0.1
+ */
+/** Adjustment is a class for adjusting string representations of values within a String. */
+public class Adjustment {
+
+    private int width;
+
+    /**
+     * Creates an adjustment.
+     *
+     * @param width is the number of positions for the result. If the width is insufficient extra
+     *     positions are added.
+     */
+    public Adjustment(int width) {
+        this.width = width;
+    }
+
+    /**
+     * Returns a centered String.
+     *
+     * @param s is the string to adjust.
+     */
+    public String center(String s) {
+        StringBuilder builder = new StringBuilder(width);
+        int fill = width - s.length();
+        for (int i = 0; i < fill / 2; i++) {
+            builder.append(' ');
+        }
+        builder.append(s);
+        for (int i = 0; i < fill - fill / 2; i++) {
+            builder.append(' ');
+        }
+        return builder.toString();
+    }
+
+    /**
+     * Returns a left adjusted String.
+     *
+     * @param s is the string to adjust.
+     */
+    public String left(String s) {
+        StringBuilder builder = new StringBuilder(width);
+        builder.append(s);
+        int fill = width - s.length();
+        for (int i = 0; i < fill; i++) {
+            builder.append(' ');
+        }
+        return builder.toString();
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param b is the value to adjust.
+     */
+    public String right(boolean b) {
+        return right(String.valueOf(b));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param c is the value to adjust.
+     */
+    public String right(char c) {
+        return right(String.valueOf(c));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(double number) {
+        return right(String.valueOf(number));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(float number) {
+        return right(String.valueOf(number));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(int number) {
+        return right(String.valueOf(number));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(long number) {
+        return right(String.valueOf(number));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param item is the value to adjust.
+     */
+    public String right(Object item) {
+        return right(String.valueOf(item));
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param s is the string to adjust.
+     */
+    public String right(String s) {
+        StringBuilder builder = new StringBuilder(width);
+        int fill = width - s.length();
+        for (int i = 0; i < fill; i++) {
+            builder.append(' ');
+        }
+        builder.append(s);
+        return builder.toString();
+    }
+}
diff --git a/app/src/main/java/util/NumberAdjustment.java b/app/src/main/java/util/NumberAdjustment.java
new file mode 100644
index 0000000..5e5db88
--- /dev/null
+++ b/app/src/main/java/util/NumberAdjustment.java
@@ -0,0 +1,123 @@
+package util;
+
+/**
+ * NumberAdjustment.java Created: Mon OTue 24 2005
+ *
+ * @author Lennart Andersson
+ * @version 0.1
+ */
+/**
+ * Adjustment is a class for adjusting string representations of numerical values within a String.
+ */
+public class NumberAdjustment extends Adjustment {
+
+    private static final double log10 = Math.log(10.0);
+    private int decimals;
+    private int exponent;
+
+    /**
+     * Creates an adjustment for numbers.
+     *
+     * @param width is the number of positions for the result. If the width is insufficient extra
+     *     positions are added.
+     * @param decimals is the number of decimals in the result.
+     */
+    public NumberAdjustment(int width, int decimals) {
+        super(width);
+        this.decimals = decimals;
+    }
+
+    /**
+     * Creates an adjustment for numbers with an exponent field.
+     *
+     * @param width is the number of positions for the result. If the width is insufficient extra
+     *     positions are added.
+     * @param decimals is the number of positions for the decimals.
+     * @param exponent is the number of positions for the exponent including the letter E. If the
+     *     width is unsufficient extra positions are added.
+     */
+    public NumberAdjustment(int width, int decimals, int exponent) {
+        this(width, decimals);
+        this.exponent = exponent;
+    }
+
+    private StringBuilder fillZero(int exp) {
+        StringBuilder builder = new StringBuilder();
+        int length = exponent;
+        if (exp < 0) {
+            builder.append('-');
+            exp = -exp;
+            length = exponent - 1;
+        }
+        String s = String.valueOf(exp);
+        for (int i = s.length(); i < length; i++) {
+            builder.append('0');
+        }
+        return builder.append(s);
+    }
+
+    private StringBuilder format(double number) {
+        StringBuilder builder = new StringBuilder();
+        long intpart = (long) number;
+        builder.append(intpart);
+        double fraction = number - intpart;
+        if (decimals > 0) {
+            builder.append('.');
+        }
+        for (int i = 0; i < decimals; i++) {
+            fraction *= 10;
+            int d = (int) fraction;
+            builder.append((char) (d + '0'));
+            fraction = fraction - d;
+        }
+        return builder;
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(double number) {
+        StringBuilder builder = new StringBuilder();
+        boolean negative = number < 0;
+        if (negative) {
+            number = -number;
+            builder.append('-');
+        }
+        if (exponent > 0) {
+            if (number == 0.0) return right(format(0.0) + "E" + fillZero(0));
+            int exp = (int) Math.floor((Math.log(number) / log10));
+            number /= Math.pow(10.0, exp);
+            number += 0.5 * Math.pow(10.0, -decimals);
+            if (number >= 10.0) {
+                number /= 10.0;
+                exp++;
+            }
+            builder.append(format(number)).append('E').append(fillZero(exp));
+        } else {
+            number += 0.5 * Math.pow(10.0, -decimals);
+            builder.append(format(number));
+        }
+        return right(builder.toString());
+    }
+
+    /**
+     * Returns a right adjusted String.
+     *
+     * @param number is the value to adjust.
+     */
+    public String right(float number) {
+        return right((double) number);
+    }
+
+    public static void main(String[] args) {
+        Adjustment adjustment = new NumberAdjustment(10, 2, 2);
+        System.out.println("0123456789");
+        System.out.println(adjustment.right(-0.0000000000000000000000000));
+        float value = (float) (1 / 3.0);
+        System.out.println(adjustment.right(value));
+        adjustment = new Adjustment(12);
+        System.out.println(adjustment.right(value));
+    }
+}
diff --git a/app/src/main/java/util/XLBufferedReader.java b/app/src/main/java/util/XLBufferedReader.java
new file mode 100644
index 0000000..308b223
--- /dev/null
+++ b/app/src/main/java/util/XLBufferedReader.java
@@ -0,0 +1,27 @@
+package util;
+
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.util.Map;
+
+// TODO move to another package
+public class XLBufferedReader extends BufferedReader {
+
+    public XLBufferedReader(String name) throws FileNotFoundException {
+        super(new FileReader(name));
+    }
+
+    // TODO Change Object to something appropriate
+    public void load(Map<String, Object> map) {
+        try {
+            while (ready()) {
+                String string = readLine();
+                int i = string.indexOf('=');
+                // TODO
+            }
+        } catch (Exception e) {
+            throw new XLException(e.getMessage());
+        }
+    }
+}
diff --git a/app/src/main/java/util/XLException.java b/app/src/main/java/util/XLException.java
new file mode 100644
index 0000000..76cb9ea
--- /dev/null
+++ b/app/src/main/java/util/XLException.java
@@ -0,0 +1,8 @@
+package util;
+
+public class XLException extends RuntimeException {
+
+    public XLException(String message) {
+        super(message);
+    }
+}
diff --git a/app/src/main/java/util/XLPrintStream.java b/app/src/main/java/util/XLPrintStream.java
new file mode 100644
index 0000000..1490357
--- /dev/null
+++ b/app/src/main/java/util/XLPrintStream.java
@@ -0,0 +1,25 @@
+package util;
+
+import java.io.FileNotFoundException;
+import java.io.PrintStream;
+import java.util.Map.Entry;
+import java.util.Set;
+
+// TODO move to another package
+public class XLPrintStream extends PrintStream {
+
+    public XLPrintStream(String fileName) throws FileNotFoundException {
+        super(fileName);
+    }
+
+    // TODO Change Object to something appropriate
+    public void save(Set<Entry<String, Object>> set) {
+        for (Entry<String, Object> entry : set) {
+            print(entry.getKey());
+            print('=');
+            println(entry.getValue());
+        }
+        flush();
+        close();
+    }
+}
diff --git a/app/src/test/resources/fibonacci.xl b/app/src/test/resources/fibonacci.xl
new file mode 100644
index 0000000..6173375
--- /dev/null
+++ b/app/src/test/resources/fibonacci.xl
@@ -0,0 +1,32 @@
+A1=1.00
+A2=1.00
+A3=A1+A2
+A4=A2+A3
+A5=A3+A4
+A6=A4+A5
+A7=A5+A6
+A8=A6+A7
+B1=A7+A8
+B2=A8+B1
+B3=B1+B2
+B4=B2+B3
+B5=B3+B4
+B6=B4+B5
+B7=B5+B6
+B8=B6+B7
+C1=B7+B8
+C2=B8+C1
+C3=C1+C2
+C4=C2+C3
+C5=C3+C4
+C6=C4+C5
+C7=C5+C6
+C8=C6+C7
+D1=C7+C8
+D2=C8+D1
+D3=D1+D2
+D4=D2+D3
+D5=D3+D4
+D6=D4+D5
+D7=D5+D6
+D8=D6+D7
diff --git a/app/src/test/resources/manual.xl b/app/src/test/resources/manual.xl
new file mode 100644
index 0000000..ed3069b
--- /dev/null
+++ b/app/src/test/resources/manual.xl
@@ -0,0 +1,6 @@
+A2=#y =
+B1=2.00
+B2=3.00
+B3=B1*B2
+A3=#x*y =
+A1=#x =
diff --git a/app/src/test/resources/omvandmanual.xl b/app/src/test/resources/omvandmanual.xl
new file mode 100644
index 0000000..b64f096
--- /dev/null
+++ b/app/src/test/resources/omvandmanual.xl
@@ -0,0 +1,6 @@
+A1=#x*y =
+A2=#x =
+A3=#y =
+B1=B2*B3
+B2=2.00
+B3=3.00
diff --git a/doc/manual.pdf b/doc/manual.pdf
new file mode 100644
index 0000000..c202b61
Binary files /dev/null and b/doc/manual.pdf differ
diff --git a/doc/overview.pdf b/doc/overview.pdf
new file mode 100644
index 0000000..c6dc499
Binary files /dev/null and b/doc/overview.pdf differ
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..2e45223
--- /dev/null
+++ b/makefile
@@ -0,0 +1,38 @@
+GITHASH := $(shell git rev-parse --short HEAD)$(shell git diff-index --quiet HEAD || echo "-dirty")
+
+TARNAME := xl-imbus-$(GITHASH).tar.gz
+
+run:
+	echo $(GITHASH)
+	./gradlew run
+
+watch:
+	./gradlew run --continuous
+
+build:
+	./gradlew build
+	#./gradlew shadowJar
+
+clean:
+	./gradlew clean
+	rm -f *.tar.gz *.tar.gz.minisig *.zip *.jpg
+
+test:
+	./gradlew test
+
+$(TARNAME):
+	git ls-files -z | xargs -0 tar -czf $(TARNAME)
+
+$(TARNAME).minisig: $(TARNAME)
+	minisign -Sm $(TARNAME)
+
+tar: $(TARNAME)
+	tar -tvf $(TARNAME)
+
+sign: $(TARNAME).minisig
+
+publish: $(TARNAME) $(TARNAME).minisig
+	scp $(TARNAME) server:/public/xl/$(TARNAME)
+	scp $(TARNAME).minisig server:/public/xl/$(TARNAME).minisig
+
+.PHONY: run watch build clean test archive sign publish