diff --git a/res/layout-port/main.xml b/res/layout-port/main.xml
index c08453ae..47c6a53d 100644
--- a/res/layout-port/main.xml
+++ b/res/layout-port/main.xml
@@ -55,7 +55,7 @@
 			<include layout="@layout/calc_eight_digit_button"/>
 			<include layout="@layout/calc_nine_digit_button"/>
 			<include layout="@layout/calc_plus_button"/>
-			<include layout="@layout/calc_paste_button"/>
+			<include layout="@layout/calc_copy_button"/>
 
 		</LinearLayout>
 
@@ -65,7 +65,7 @@
 			<include layout="@layout/calc_zero_digit_button"/>
 			<include layout="@layout/calc_square_brackets_button"/>
 			<include layout="@layout/calc_subtraction_button"/>
-			<include layout="@layout/calc_copy_button"/>
+			<include layout="@layout/calc_paste_button"/>
 
 		</LinearLayout>
 
diff --git a/res/layout/calc_clear_button.xml b/res/layout/calc_clear_button.xml
index b23a7d5a..da1af738 100644
--- a/res/layout/calc_clear_button.xml
+++ b/res/layout/calc_clear_button.xml
@@ -6,9 +6,9 @@
   ~ or visit http://se.solovyev.org
   -->
 
-<org.solovyev.android.view.widgets.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
-													   xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/clearButton"
-													   a:text="@string/c_clear"
-													   style="@style/control_button_style"
-													   a:onClick="clearButtonClickHandler"/>
\ No newline at end of file
+<org.solovyev.android.view.widgets.ColorButton xmlns:a="http://schemas.android.com/apk/res/android"
+			 xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
+			 a:id="@+id/clearButton"
+			 a:drawableTop="@drawable/ic_delete"
+			 style="@style/control_image_button_style"
+			 a:onClick="clearButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_copy_button.xml b/res/layout/calc_copy_button.xml
index 4ed715d9..f355567c 100644
--- a/res/layout/calc_copy_button.xml
+++ b/res/layout/calc_copy_button.xml
@@ -6,10 +6,9 @@
   ~ or visit http://se.solovyev.org
   -->
 
-<ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
+<org.solovyev.android.view.widgets.ColorButton xmlns:a="http://schemas.android.com/apk/res/android"
 			 xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 			 a:id="@+id/pasteButton"
-			 a:src="@drawable/copy"
-			 style="@style/control_button_style"
-			 a:padding="6dp"
+			 a:drawableTop="@drawable/copy"
+			 style="@style/control_image_button_style"
 			 a:onClick="copyButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_donate_button.xml b/res/layout/calc_donate_button.xml
index f365af31..dd1f0f2e 100644
--- a/res/layout/calc_donate_button.xml
+++ b/res/layout/calc_donate_button.xml
@@ -10,6 +10,5 @@
 			 xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 			 a:id="@+id/pasteButton"
 			 a:src="@drawable/heart"
-			 style="@style/control_button_style"
-			 a:padding="6dp"
+			 style="@style/control_image_button_style"
 			 a:onClick="donateButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_erase_button.xml b/res/layout/calc_erase_button.xml
index 13d49758..bf6c7057 100644
--- a/res/layout/calc_erase_button.xml
+++ b/res/layout/calc_erase_button.xml
@@ -6,9 +6,9 @@
   ~ or visit http://se.solovyev.org
   -->
 
-<org.solovyev.android.view.widgets.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
-													   xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/eraseButton"
-													   a:text="@string/c_erase"
-													   style="@style/control_button_style"
-													   a:onClick="eraseButtonClickHandler"/>
\ No newline at end of file
+<org.solovyev.android.view.widgets.ColorButton xmlns:a="http://schemas.android.com/apk/res/android"
+			 xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
+			 a:id="@+id/eraseButton"
+			 a:drawableTop="@drawable/sym_keyboard_delete"
+			 style="@style/control_image_button_style"
+			 a:onClick="eraseButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_paste_button.xml b/res/layout/calc_paste_button.xml
index e2d73b8c..d592b9f8 100644
--- a/res/layout/calc_paste_button.xml
+++ b/res/layout/calc_paste_button.xml
@@ -6,10 +6,9 @@
   ~ or visit http://se.solovyev.org
   -->
 
-<ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
+<org.solovyev.android.view.widgets.ColorButton xmlns:a="http://schemas.android.com/apk/res/android"
 			 xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 			 a:id="@+id/pasteButton"
-			 a:src="@drawable/paste"
-			 style="@style/control_button_style"
-			 a:padding="6dp"
+			 a:drawableTop="@drawable/paste"
+			 style="@style/control_image_button_style"
 			 a:onClick="pasteButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_round_brackets_button.xml b/res/layout/calc_round_brackets_button.xml
index e721bedc..b1f780ed 100644
--- a/res/layout/calc_round_brackets_button.xml
+++ b/res/layout/calc_round_brackets_button.xml
@@ -10,5 +10,6 @@
 													   xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 													   a:id="@+id/roundBracketsButton" a:text="()"
 													   calc:textUp="("
-													   calc:textDown=")" style="@style/digit_button_style"
+													   calc:textDown=")"
+													   style="@style/digit_button_style"
 													   a:onClick="digitButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_square_brackets_button.xml b/res/layout/calc_square_brackets_button.xml
index 360d83aa..f23abd5c 100644
--- a/res/layout/calc_square_brackets_button.xml
+++ b/res/layout/calc_square_brackets_button.xml
@@ -10,5 +10,6 @@
 													   xmlns:calc="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 													   a:id="@+id/squareBracketsButton" a:text="[]"
 													   calc:textUp="["
-													   calc:textDown="]" style="@style/digit_button_style"
+													   calc:textDown="]"
+													   style="@style/digit_button_style"
 													   a:onClick="digitButtonClickHandler"/>
\ No newline at end of file
diff --git a/res/layout/calc_vars_button.xml b/res/layout/calc_vars_button.xml
index 78efa2b0..ec814a4d 100644
--- a/res/layout/calc_vars_button.xml
+++ b/res/layout/calc_vars_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.widgets.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   a:id="@+id/varsButton"
-													   a:text="π,e,…"
+													   a:text="π,…"
 													   a:textStyle="italic"
 													   a:onClick="varsButtonClickHandler"
 													   style="@style/control_button_style"/>
\ No newline at end of file
diff --git a/res/layout/vars.xml b/res/layout/vars.xml
new file mode 100644
index 00000000..1e66cacb
--- /dev/null
+++ b/res/layout/vars.xml
@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  ~ Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+  ~ For more information, please, contact se.solovyev@gmail.com
+  ~ or visit http://se.solovyev.org
+  -->
+
+<LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
+    a:orientation="vertical"
+    a:layout_width="match_parent"
+    a:layout_height="match_parent">
+
+    <ListView
+        a:layout_width="match_parent"
+        a:layout_height="match_parent"
+        a:layout_weight="1"
+        a:id="@android:id/list"/>
+
+    <Button
+        a:layout_width="wrap_content"
+        a:layout_height="wrap_content"
+        a:layout_gravity="center_horizontal"
+        a:text="@string/c_add"
+		a:paddingLeft="40dp"
+		a:paddingRight="40dp"
+        a:onClick="addVarButtonClickHandler"/>
+
+</LinearLayout>
\ No newline at end of file
diff --git a/res/values-ru/strings.xml b/res/values-ru/strings.xml
index 0f01faae..6dcb2b49 100644
--- a/res/values-ru/strings.xml
+++ b/res/values-ru/strings.xml
@@ -20,7 +20,7 @@
 
 	<!--ABOUT ACTIVITY-->
 	<string name="c_copyright">Copyright (c) 2009-2011\n\n<b>Программа создана\nserso aka se.solovyev</b>\n\n
-		Эта программа бесплатна и открыта.\nИсходный код может быть найден на \n<a href="https://github.com/serso/android_calculator">http://github.com</a>\n\n
+		Эта программа с открытыми исходным кодом:\nон может быть найден на \n<a href="https://github.com/serso/android_calculator">http://github.com</a>\n\n
 		За подробной информацией, пожалуйста,\nобращайтесь на почту\n<a href="mailto:se.solovyev@gmail.com">se.solovyev@gmail.com</a>\n
 		или посетите сайт \n<a href="http://se.solovyev.org">http://se.solovyev.org</a>\n\n
 		Если вы хотите поддержать проект материально\nвы можете сделать это через \n<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&amp;business=se%2esolovyev%40gmail%2ecom&amp;lc=RU&amp;item_name=Android%20Calculator&amp;currency_code=USD&amp;bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted">http://paypal.com</a>
@@ -55,9 +55,10 @@
 	<string name="c_sys.var.cannot.be.changed">Системная переменная не может быть изменена!</string>
 
 	<string name="c_pi_description">Отношение длины окружности к диаметру</string>
-	<string name="c_e_description">Вещесвтенное число, такое что производная функции f(x) = e^x в точке x = 0 равно 1
-	</string>
+	<string name="c_e_description">Вещесвтенное число, такое что производная функции f(x) = e^x в точке x = 0 равно 1</string>
 	<string name="c_i_description">Мнимая единица, определённая как i^2 = −1</string>
+	<string name="c_nan_description">Не число</string>
+	<string name="c_infinity_description">Бесконечность</string>
 	<string name="c_calc_editor_hint">Введите новое выражение</string>
 	<string name="c_continue">Продолжить</string>
 	<string name="c_press_to_copy">Нажмите для копирования</string>
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 45a9226a..37992ffe 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -21,7 +21,7 @@
 
 	<!--ABOUT ACTIVITY-->
 	<string name="c_copyright">Copyright (c) 2009-2011\n\n<b>Created by serso aka se.solovyev</b>\n\n
-		This program is free and open source.\nSource code can be found on\n<a href="https://github.com/serso/android_calculator">http://github.com</a>\n\n
+		This program is open source:\nall source code can be found on\n<a href="https://github.com/serso/android_calculator">http://github.com</a>\n\n
 		For more information please\ncontact the author by email\n<a href="mailto:se.solovyev@gmail.com">se.solovyev@gmail.com</a>
 		\nor visit\n<a href="http://se.solovyev.org">http://se.solovyev.org</a>\n\n
 		If you want to support the project\nyou can donate money via\n<a href="https://www.paypal.com/cgi-bin/webscr?cmd=_donations&amp;business=se%2esolovyev%40gmail%2ecom&amp;lc=RU&amp;item_name=Android%20Calculator&amp;currency_code=USD&amp;bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted">http://paypal.com</a>
@@ -29,8 +29,8 @@
 
 	<string name="c_undo">undo</string>
 	<string name="c_redo">redo</string>
-	<string name="c_clear">CE</string>
-	<string name="c_erase">C</string>
+	<string name="c_clear">clear all</string>
+	<string name="c_erase">clear</string>
 	<string name="c_paste">paste</string>
 	<string name="c_vars">vars</string>
 
@@ -60,6 +60,9 @@
 	<string name="c_pi_description">Ratio of any circle\'s circumference to its diameter</string>
 	<string name="c_e_description">Unique real number such that the value of the derivative (slope of the tangent line) of the function f(x) = e^x at the point x = 0 is equal to 1</string>
 	<string name="c_i_description">Imaginary unit, defined such that i^2 = −1</string>
+	<string name="c_nan_description">Not a number</string>
+	<string name="c_infinity_description">Infinity</string>
+
 	<string name="c_calc_editor_hint">Enter new expression</string>
 	<string name="c_press_to_copy">Press to copy</string>
 	<string name="c_continue">Continue</string>
diff --git a/res/values/styles.xml b/res/values/styles.xml
index 7ea9c018..c3bcfbe8 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -1,50 +1,50 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
 
-    <style name="editTextInputStyle">
-        <item name="android:layout_width">fill_parent</item>
-        <item name="android:layout_height">wrap_content</item>
-        <item name="android:typeface">monospace</item>
-    </style>
+	<style name="editTextInputStyle">
+		<item name="android:layout_width">fill_parent</item>
+		<item name="android:layout_height">wrap_content</item>
+		<item name="android:typeface">monospace</item>
+	</style>
 
-    <style name="button_style">
-        <item name="android:layout_width">match_parent</item>
-        <item name="android:layout_height">match_parent</item>
-        <item name="android:layout_weight">1</item>
-        <item name="android:focusable">true</item>
-        <item name="android:background">@drawable/button</item>
-        <item name="android:layout_marginLeft">1dp</item>
-    </style>
+	<style name="button_style">
+		<item name="android:layout_width">match_parent</item>
+		<item name="android:layout_height">match_parent</item>
+		<item name="android:layout_weight">1</item>
+		<item name="android:focusable">true</item>
+		<item name="android:textSize">20dp</item>
+		<item name="android:background">@drawable/button</item>
+		<item name="android:layout_marginLeft">1dp</item>
+	</style>
 
-    <style name="digit_button_style" parent="button_style">
-        <item name="android:background">@drawable/blue_button</item>
-    </style>
+	<style name="digit_button_style" parent="button_style">
+		<item name="android:background">@drawable/blue_button</item>
+	</style>
 
 	<style name="control_button_style" parent="button_style"/>
-
-    <style name="button_small_style" parent="button_style">
-        <item name="android:textSize">30dp</item>
-    </style>
+	<style name="control_image_button_style" parent="control_button_style">
+		<item name="android:padding">6dp</item>
+	</style>
 
 	<style name="editor_style">
-        <item name="android:textSize">25dp</item>
-        <item name="android:background">#000000</item>
-        <item name="android:textColor">@color/text_color</item>
-        <item name="android:gravity">left|top</item>
+		<item name="android:textSize">25dp</item>
+		<item name="android:background">#000000</item>
+		<item name="android:textColor">@color/text_color</item>
+		<item name="android:gravity">left|top</item>
 		<item name="android:padding">5dp</item>
-        <item name="android:layout_width">match_parent</item>
-        <item name="android:layout_height">match_parent</item>
-    </style>
+		<item name="android:layout_width">match_parent</item>
+		<item name="android:layout_height">match_parent</item>
+	</style>
 
-    <style name="display_style">
-        <item name="android:textSize">25dp</item>
-        <item name="android:background">#000000</item>
-        <item name="android:textColor">@color/text_color</item>
-        <item name="android:gravity">right|center_vertical</item>
+	<style name="display_style">
+		<item name="android:textSize">25dp</item>
+		<item name="android:background">#000000</item>
+		<item name="android:textColor">@color/text_color</item>
+		<item name="android:gravity">right|center_vertical</item>
 		<item name="android:padding">5dp</item>
-        <item name="android:layout_width">match_parent</item>
-        <item name="android:layout_height">match_parent</item>
-    </style>
+		<item name="android:layout_width">match_parent</item>
+		<item name="android:layout_height">match_parent</item>
+	</style>
 
 	<style name="about_style">
 		<item name="android:textSize">15dp</item>
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java b/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
index 25c9edab..2eebe0a8 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorEditor.java
@@ -13,7 +13,8 @@ import android.util.Log;
 import android.view.ContextMenu;
 import android.widget.EditText;
 import org.jetbrains.annotations.NotNull;
-import org.solovyev.android.calculator.math.MathType;
+import org.solovyev.android.calculator.model.ParseException;
+import org.solovyev.android.calculator.model.TextProcessor;
 
 /**
  * User: serso
@@ -24,10 +25,8 @@ public class CalculatorEditor extends EditText {
 
 	private boolean highlightText = true;
 
-	private final static int BASE_COLOUR = Color.WHITE;
-	private final static int BASE_COLOUR_RED_COMPONENT = Color.red(BASE_COLOUR);
-	private final static int BASE_COLOUR_GREEN_COMPONENT = Color.green(BASE_COLOUR);
-	private final static int BASE_COLOUR_BLUE_COMPONENT = Color.blue(BASE_COLOUR);
+	@NotNull
+	private final static TextProcessor textHighlighter = new TextHighlighter(Color.WHITE);
 
 	public CalculatorEditor(Context context) {
 		super(context);
@@ -54,9 +53,7 @@ public class CalculatorEditor extends EditText {
 		menu.removeItem(android.R.id.startSelectingText);
 	}
 
-
-
-	public void redraw() {
+	public synchronized void redraw() {
 		String text = getText().toString();
 
 		int selectionStart = getSelectionStart();
@@ -64,107 +61,24 @@ public class CalculatorEditor extends EditText {
 
 		if (highlightText) {
 
-			text = highlightText(text);
+			Log.d(this.getClass().getName(), text);
 
+			try {
+				text = textHighlighter.process(text);
+			} catch (ParseException e) {
+				Log.e(this.getClass().getName(), e.getMessage(), e);
+			}
+
+			Log.d(this.getClass().getName(), text);
 			super.setText(Html.fromHtml(text), BufferType.EDITABLE);
 		} else {
 			super.setText(text, BufferType.EDITABLE);
 		}
 
+		Log.d(this.getClass().getName(), getText().toString());
 		setSelection(selectionStart, selectionEnd);
 	}
 
-	private String highlightText(@NotNull final String text) {
-		final String result;
-
-		int maxNumberOfOpenGroupSymbols = 0;
-		int numberOfOpenGroupSymbols = 0;
-
-		final StringBuilder text1 = new StringBuilder();
-
-		for (int i = 0; i < text.length(); i++) {
-			final MathType.Result mathType = MathType.getType(text, i);
-
-			switch (mathType.getMathType()) {
-				case open_group_symbol:
-					numberOfOpenGroupSymbols++;
-					maxNumberOfOpenGroupSymbols = Math.max(maxNumberOfOpenGroupSymbols, numberOfOpenGroupSymbols);
-					text1.append(text.charAt(i));
-					break;
-				case close_group_symbol:
-					numberOfOpenGroupSymbols--;
-					text1.append(text.charAt(i));
-					break;
-				case function:
-					i = processHighlightedText(text1, i, mathType.getMatch(), "i");
-					break;
-				case constant:
-					i = processHighlightedText(text1, i, mathType.getMatch(), "b");
-					break;
-				default:
-					text1.append(text.charAt(i));
-			}
-		}
-
-		if (maxNumberOfOpenGroupSymbols > 0) {
-
-			final StringBuilder text2 = new StringBuilder();
-
-			processBracketGroup(text2, text1.toString(), 0, 0, maxNumberOfOpenGroupSymbols);
-
-			Log.d(CalculatorEditor.class.getName(), text2.toString());
-
-			result = text2.toString();
-		} else {
-			result = text1.toString();
-		}
-
-		return result;
-	}
-
-	private int processHighlightedText(@NotNull StringBuilder result, int i, @NotNull String functionName, @NotNull String tag) {
-		result.append("<").append(tag).append(">").append(functionName).append("</").append(tag).append(">");
-		return i + functionName.length() - 1;
-	}
-
-	private int processBracketGroup(@NotNull StringBuilder result, @NotNull String s, int i, int numberOfOpenings, int maxNumberOfGroups) {
-
-		result.append("<font color=\"").append(getColor(maxNumberOfGroups, numberOfOpenings)).append("\">");
-
-		for (; i < s.length(); i++) {
-			char ch = s.charAt(i);
-
-			if (MathType.openGroupSymbols.contains(ch)) {
-				result.append(ch);
-				result.append("</font>");
-				i = processBracketGroup(result, s, i + 1, numberOfOpenings + 1, maxNumberOfGroups);
-				result.append("<font color=\"").append(getColor(maxNumberOfGroups, numberOfOpenings)).append("\">");
-				if (i < s.length() && MathType.closeGroupSymbols.contains(s.charAt(i))) {
-					result.append(s.charAt(i));
-				}
-			} else if (MathType.closeGroupSymbols.contains(ch)) {
-				break;
-			} else {
-				result.append(ch);
-			}
-		}
-
-		result.append("</font>");
-
-
-		return i;
-	}
-
-	private String getColor(int numberOfOpenGroupSymbols, int numberOfOpenings) {
-		double c = 0.7;
-
-		int offset = ((int) (255 * c)) * numberOfOpenings / (numberOfOpenGroupSymbols + 1);
-
-		int result = Color.rgb(BASE_COLOUR_RED_COMPONENT - offset, BASE_COLOUR_GREEN_COMPONENT - offset, BASE_COLOUR_BLUE_COMPONENT - offset);
-
-		return "#" + Integer.toHexString(result).substring(2);
-	}
-
 	public boolean isHighlightText() {
 		return highlightText;
 	}
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorVarsActivity.java b/src/main/java/org/solovyev/android/calculator/CalculatorVarsActivity.java
index df9eb7ef..53185070 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorVarsActivity.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorVarsActivity.java
@@ -39,6 +39,8 @@ public class CalculatorVarsActivity extends ListActivity {
 	protected void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
+		setContentView(R.layout.vars);
+
 		adapter = new VarsArrayAdapter(this, R.layout.var, R.id.var_text, new ArrayList<Var>(CalculatorModel.instance.getVarsRegister().getVars()));
 		setListAdapter(adapter);
 
@@ -68,6 +70,12 @@ public class CalculatorVarsActivity extends ListActivity {
 
 	}
 
+	@SuppressWarnings({"UnusedDeclaration"})
+	public void addVarButtonClickHandler(@NotNull View v) {
+		createEditVariableDialog(null, null, null, null);
+	}
+
+
 	private void createEditVariableDialog(@Nullable final Var var, @Nullable final String name, @Nullable final String value, @Nullable final String description) {
 		if (var == null || !var.isSystem()) {
 
diff --git a/src/main/java/org/solovyev/android/calculator/CalculatorView.java b/src/main/java/org/solovyev/android/calculator/CalculatorView.java
index a1443792..9b115868 100644
--- a/src/main/java/org/solovyev/android/calculator/CalculatorView.java
+++ b/src/main/java/org/solovyev/android/calculator/CalculatorView.java
@@ -107,7 +107,7 @@ public class CalculatorView implements CursorControl, HistoryControl<CalculatorH
 	@NotNull
 	private final MutableObject<Runnable> currentRunner = new MutableObject<Runnable>();
 
-	public void doTextOperation(@NotNull TextOperation operation) {
+	public synchronized void doTextOperation(@NotNull TextOperation operation) {
 		final String editorStateBefore = this.editor.getText().toString();
 
 		operation.doOperation(this.editor);
diff --git a/src/main/java/org/solovyev/android/calculator/TextHighlighter.java b/src/main/java/org/solovyev/android/calculator/TextHighlighter.java
new file mode 100644
index 00000000..2b8364ac
--- /dev/null
+++ b/src/main/java/org/solovyev/android/calculator/TextHighlighter.java
@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator;
+
+import android.graphics.Color;
+import org.jetbrains.annotations.NotNull;
+import org.solovyev.android.calculator.math.MathType;
+import org.solovyev.android.calculator.model.ParseException;
+import org.solovyev.android.calculator.model.TextProcessor;
+
+/**
+ * User: serso
+ * Date: 10/12/11
+ * Time: 9:47 PM
+ */
+public class TextHighlighter implements TextProcessor {
+
+	private final int color;
+	private final int colorRed;
+	private final int colorGreen;
+	private final int colorBlue;
+
+	public TextHighlighter(int baseColor) {
+		this.color = baseColor;
+		this.colorRed = Color.red(baseColor);
+		this.colorGreen = Color.green(baseColor);
+		this.colorBlue = Color.blue(baseColor);
+	}
+
+	@NotNull
+	@Override
+	public String process(@NotNull String text) throws ParseException {
+		final String result;
+
+		int maxNumberOfOpenGroupSymbols = 0;
+		int numberOfOpenGroupSymbols = 0;
+
+		final StringBuilder text1 = new StringBuilder();
+
+		for (int i = 0; i < text.length(); i++) {
+			final MathType.Result mathType = MathType.getType(text, i);
+
+			switch (mathType.getMathType()) {
+				case open_group_symbol:
+					numberOfOpenGroupSymbols++;
+					maxNumberOfOpenGroupSymbols = Math.max(maxNumberOfOpenGroupSymbols, numberOfOpenGroupSymbols);
+					text1.append(text.charAt(i));
+					break;
+				case close_group_symbol:
+					numberOfOpenGroupSymbols--;
+					text1.append(text.charAt(i));
+					break;
+				case function:
+					i = processHighlightedText(text1, i, mathType.getMatch(), "i");
+					break;
+				case constant:
+					i = processHighlightedText(text1, i, mathType.getMatch(), "b");
+					break;
+				default:
+					text1.append(text.charAt(i));
+			}
+		}
+
+		if (maxNumberOfOpenGroupSymbols > 0) {
+
+			final StringBuilder text2 = new StringBuilder();
+
+			String s = text1.toString();
+			int i = processBracketGroup(text2, s, 0, 0, maxNumberOfOpenGroupSymbols);
+			for (; i < s.length(); i++) {
+				text2.append(s.charAt(i));
+			}
+
+			//Log.d(CalculatorEditor.class.getName(), text2.toString());
+
+			result = text2.toString();
+		} else {
+			result = text1.toString();
+		}
+
+		return result;
+	}
+
+	private int processHighlightedText(@NotNull StringBuilder result, int i, @NotNull String functionName, @NotNull String tag) {
+		result.append("<").append(tag).append(">").append(functionName).append("</").append(tag).append(">");
+		return i + functionName.length() - 1;
+	}
+
+	private int processBracketGroup(@NotNull StringBuilder result, @NotNull String s, int i, int numberOfOpenings, int maxNumberOfGroups) {
+
+		result.append("<font color=\"").append(getColor(maxNumberOfGroups, numberOfOpenings)).append("\">");
+
+		for (; i < s.length(); i++) {
+			char ch = s.charAt(i);
+
+			if (MathType.openGroupSymbols.contains(ch)) {
+				result.append(ch);
+				result.append("</font>");
+				i = processBracketGroup(result, s, i + 1, numberOfOpenings + 1, maxNumberOfGroups);
+				result.append("<font color=\"").append(getColor(maxNumberOfGroups, numberOfOpenings)).append("\">");
+				if (i < s.length() && MathType.closeGroupSymbols.contains(s.charAt(i))) {
+					result.append(s.charAt(i));
+				}
+			} else if (MathType.closeGroupSymbols.contains(ch)) {
+				break;
+			} else {
+				result.append(ch);
+			}
+		}
+
+		result.append("</font>");
+
+
+		return i;
+	}
+
+	private String getColor(int totalNumberOfOpenings, int numberOfOpenings) {
+		double c = 0.8;
+
+		int offset = ((int) (255 * c)) * numberOfOpenings / (totalNumberOfOpenings + 1);
+
+		// for tests:
+		// innt result = Color.rgb(BASE_COLOUR_RED_COMPONENT - offset, BASE_COLOUR_GREEN_COMPONENT - offset, BASE_COLOUR_BLUE_COMPONENT - offset);
+		int result = (0xFF << 24) | ((colorRed - offset) << 16) | ((colorGreen - offset) << 8) | (colorBlue - offset);
+
+		return "#" + Integer.toHexString(result).substring(2);
+	}
+}
diff --git a/src/main/java/org/solovyev/android/calculator/math/Functions.java b/src/main/java/org/solovyev/android/calculator/math/Functions.java
index 9e481950..389290cb 100644
--- a/src/main/java/org/solovyev/android/calculator/math/Functions.java
+++ b/src/main/java/org/solovyev/android/calculator/math/Functions.java
@@ -37,6 +37,7 @@ public class Functions {
 	public final static String EXP = "exp";
 	public final static String SQRT_SIGN = "√";
 	public final static String SQRT = "sqrt";
+
 	public final static String E = "E";
 	public final static String E_POWER = "10^";
 
diff --git a/src/main/java/org/solovyev/android/calculator/math/MathType.java b/src/main/java/org/solovyev/android/calculator/math/MathType.java
index 80c2ab40..32e1eaf7 100644
--- a/src/main/java/org/solovyev/android/calculator/math/MathType.java
+++ b/src/main/java/org/solovyev/android/calculator/math/MathType.java
@@ -34,8 +34,11 @@ public enum MathType {
 	public static final String IMAGINARY_NUMBER_DEF = "sqrt(-1)";
 	public static final String PI = "π";
 	public static final String E = "e";
+	public final static String NAN = "NaN";
+	public final static String INFINITY = "∞";
+	public final static String INFINITY_DEF = "Infinity";
 
-	public static final List<String> constants = Arrays.asList(E, PI, IMAGINARY_NUMBER);
+	public static final List<String> constants = Arrays.asList(E, PI, IMAGINARY_NUMBER, NAN, INFINITY);
 
 	public static final List<String> digits = Arrays.asList("0", "1", "2", "3", "4", "5", "6", "7", "8", "9");
 
diff --git a/src/main/java/org/solovyev/android/calculator/model/FromJsclTextProcessor.java b/src/main/java/org/solovyev/android/calculator/model/FromJsclTextProcessor.java
index 4db3ea06..71316548 100644
--- a/src/main/java/org/solovyev/android/calculator/model/FromJsclTextProcessor.java
+++ b/src/main/java/org/solovyev/android/calculator/model/FromJsclTextProcessor.java
@@ -22,7 +22,12 @@ class FromJsclTextProcessor implements TextProcessor {
 	@Override
 	public String process(@NotNull String result) throws ParseException {
 		try {
-			result = String.valueOf(round(result));
+			final Double roundedValue = round(result);
+			if ( roundedValue.isInfinite() ) {
+				result =  MathType.INFINITY;
+			} else {
+				result = String.valueOf(roundedValue);
+			}
 		} catch (NumberFormatException e) {
 			if (result.contains(MathType.IMAGINARY_NUMBER_DEF)) {
 				try {
diff --git a/src/main/java/org/solovyev/android/calculator/model/VarsRegisterImpl.java b/src/main/java/org/solovyev/android/calculator/model/VarsRegisterImpl.java
index c07847fc..2d15524d 100644
--- a/src/main/java/org/solovyev/android/calculator/model/VarsRegisterImpl.java
+++ b/src/main/java/org/solovyev/android/calculator/model/VarsRegisterImpl.java
@@ -144,7 +144,7 @@ class VarsRegisterImpl implements VarsRegister {
 			final Var.Builder builder;
 			final Integer varDescription;
 
-			if ( systemVarName.equals(MathType.E) ){
+			if (systemVarName.equals(MathType.E)) {
 				builder = new Var.Builder(systemVarName, Math.E);
 				varDescription = R.string.c_e_description;
 			} else if (systemVarName.equals(MathType.PI)) {
@@ -153,6 +153,12 @@ class VarsRegisterImpl implements VarsRegister {
 			} else if (systemVarName.equals(MathType.IMAGINARY_NUMBER)) {
 				builder = new Var.Builder(systemVarName, MathType.IMAGINARY_NUMBER_DEF);
 				varDescription = R.string.c_i_description;
+			} else if (systemVarName.equals(MathType.NAN)) {
+				builder = new Var.Builder(systemVarName, MathType.NAN);
+				varDescription = R.string.c_nan_description;
+			} else if (systemVarName.equals(MathType.INFINITY)) {
+				builder = new Var.Builder(systemVarName, MathType.INFINITY_DEF);
+				varDescription = R.string.c_infinity_description;
 			} else {
 				throw new IllegalArgumentException(systemVarName + " is not supported yet!");
 			}
diff --git a/src/main/java/org/solovyev/android/view/widgets/ColorButton.java b/src/main/java/org/solovyev/android/view/widgets/ColorButton.java
index 0057f870..bcdc87fc 100644
--- a/src/main/java/org/solovyev/android/view/widgets/ColorButton.java
+++ b/src/main/java/org/solovyev/android/view/widgets/ColorButton.java
@@ -26,6 +26,7 @@ import android.content.res.Resources;
 import android.graphics.Canvas;
 import android.graphics.Paint;
 import android.graphics.Paint.Style;
+import android.graphics.drawable.Drawable;
 import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.widget.Button;
@@ -33,6 +34,7 @@ import org.jetbrains.annotations.NotNull;
 import org.solovyev.android.calculator.R;
 import org.solovyev.android.view.FontSizeAdjuster;
 import org.solovyev.common.utils.Point2d;
+import org.solovyev.common.utils.StringUtils;
 
 /**
  * NOTE: copied from com.android.calculator2.ColorButton
@@ -42,14 +44,15 @@ import org.solovyev.common.utils.Point2d;
  * Button with click-animation effect.
  */
 public class ColorButton extends Button {
-	int CLICK_FEEDBACK_COLOR;
-	static final int CLICK_FEEDBACK_INTERVAL = 10;
-	static final int CLICK_FEEDBACK_DURATION = 350;
+
+	private int CLICK_FEEDBACK_COLOR;
+	private static final int CLICK_FEEDBACK_INTERVAL = 10;
+	private static final int CLICK_FEEDBACK_DURATION = 350;
 
 	@NotNull
 	private Point2d textPosition;
-	private long mAnimStart;
-	private Paint mFeedbackPaint;
+	private long animationStart;
+	private Paint feedbackPaint;
 
 	public ColorButton(Context context, AttributeSet attrs) {
 		this(context, attrs, true);
@@ -66,12 +69,12 @@ public class ColorButton extends Button {
 		Resources res = getResources();
 
 		CLICK_FEEDBACK_COLOR = res.getColor(org.solovyev.android.calculator.R.color.magic_flame);
-		mFeedbackPaint = new Paint();
-		mFeedbackPaint.setStyle(Style.STROKE);
-		mFeedbackPaint.setStrokeWidth(2);
+		feedbackPaint = new Paint();
+		feedbackPaint.setStyle(Style.STROKE);
+		feedbackPaint.setStrokeWidth(2);
 		getPaint().setColor(res.getColor(R.color.button_text_color));
 
-		mAnimStart = -1;
+		animationStart = -1;
 
 		if (context instanceof FontSizeAdjuster) {
 			((FontSizeAdjuster) context).adjustFontSize(this);
@@ -113,17 +116,17 @@ public class ColorButton extends Button {
 		int alpha = 255 - 255 * duration / CLICK_FEEDBACK_DURATION;
 		int color = CLICK_FEEDBACK_COLOR | (alpha << 24);
 
-		mFeedbackPaint.setColor(color);
-		canvas.drawRect(1, 1, getWidth() - 1, getHeight() - 1, mFeedbackPaint);
+		feedbackPaint.setColor(color);
+		canvas.drawRect(1, 1, getWidth() - 1, getHeight() - 1, feedbackPaint);
 	}
 
 	@Override
 	public void onDraw(Canvas canvas) {
-		if (mAnimStart != -1) {
-			int animDuration = (int) (System.currentTimeMillis() - mAnimStart);
+		if (animationStart != -1) {
+			int animDuration = (int) (System.currentTimeMillis() - animationStart);
 
 			if (animDuration >= CLICK_FEEDBACK_DURATION) {
-				mAnimStart = -1;
+				animationStart = -1;
 			} else {
 				drawMagicFlame(animDuration, canvas);
 				postInvalidateDelayed(CLICK_FEEDBACK_INTERVAL);
@@ -131,13 +134,48 @@ public class ColorButton extends Button {
 		}
 
 		CharSequence text = getText();
-		if (text != null && textPosition != null) {
+		if (!StringUtils.isEmpty(text) && textPosition != null) {
 			canvas.drawText(text, 0, text.length(), textPosition.getX(), textPosition.getY(), getPaint());
+		} else {
+			drawDrawables(canvas);
+		}
+	}
+
+	private void drawDrawables(Canvas canvas) {
+		final int compoundPaddingLeft = getCompoundPaddingLeft();
+		final int compoundPaddingTop = getCompoundPaddingTop();
+		final int compoundPaddingRight = getCompoundPaddingRight();
+		final int compoundPaddingBottom = getCompoundPaddingBottom();
+
+		final int scrollX = getScrollX();
+		final int scrollY = getScrollY();
+
+		final int right = getRight();
+		final int left = getLeft();
+		final int bottom = getBottom();
+		final int top = getTop();
+
+		final Drawable[] drawables = getCompoundDrawables();
+		if (drawables != null) {
+
+			int vspace = bottom - top - compoundPaddingBottom - compoundPaddingTop;
+			int hspace = right - left - compoundPaddingRight - compoundPaddingLeft;
+
+			Drawable topDr = drawables[1];
+			// IMPORTANT: The coordinates computed are also used in invalidateDrawable()
+			// Make sure to update invalidateDrawable() when changing this code.
+			if (topDr != null) {
+				canvas.save();
+				canvas.translate(scrollX + compoundPaddingLeft + (hspace - topDr.getBounds().width()) / 2,
+                        scrollY + getPaddingTop() + vspace / 2);
+				topDr.draw(canvas);
+				canvas.restore();
+			}
 		}
 	}
 
 	public void animateClickFeedback() {
-		mAnimStart = System.currentTimeMillis();
+		animationStart = System.currentTimeMillis();
 		invalidate();
 	}
 
diff --git a/src/main/java/org/solovyev/android/view/widgets/DirectionDragButton.java b/src/main/java/org/solovyev/android/view/widgets/DirectionDragButton.java
index 1a41e425..48e1b777 100644
--- a/src/main/java/org/solovyev/android/view/widgets/DirectionDragButton.java
+++ b/src/main/java/org/solovyev/android/view/widgets/DirectionDragButton.java
@@ -126,11 +126,10 @@ public class DirectionDragButton extends DragButton {
 
 		basePaint.measureText(StringUtils.getNotEmpty(baseText, "|"));
 
-		float height = h - basePaint.ascent() - basePaint.descent();
 		if (direction < 0) {
-			result.setY(height / 2 + height / 3 + selfHeight);
+			result.setY(h / 2 + h / 3 - selfHeight / 2);
 		} else {
-			result.setY(height / 2 - height / 3);
+			result.setY(h / 2 - h / 3 - selfHeight / 2);
 		}
 
 		return result;
@@ -158,7 +157,7 @@ public class DirectionDragButton extends DragButton {
 
 		upDownTextPaint = new TextPaint(paint);
 		upDownTextPaint.setAlpha(150);
-		upDownTextPaint.setTextSize(paint.getTextSize() / 2);
+		upDownTextPaint.setTextSize(paint.getTextSize() / 3);
 	}
 
 	private String getStyledUpDownText(@Nullable String text) {
diff --git a/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java b/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java
new file mode 100644
index 00000000..029d15aa
--- /dev/null
+++ b/src/test/java/org/solovyev/android/calculator/TextHighlighterTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator;
+
+import junit.framework.Assert;
+import org.junit.Test;
+import org.solovyev.android.calculator.model.TextProcessor;
+
+import java.util.Date;
+import java.util.Random;
+
+/**
+ * User: serso
+ * Date: 10/12/11
+ * Time: 10:07 PM
+ */
+public class TextHighlighterTest {
+
+	@Test
+	public void testProcess() throws Exception {
+		final TextProcessor textHighlighter = new TextHighlighter(0);
+
+		final Random random = new Random(new Date().getTime());
+		for (int i = 0; i < 1000; i++) {
+			final StringBuilder sb = new StringBuilder();
+			for (int j = 0; j < 1000; j++) {
+				sb.append(random.nextBoolean() ? "(" : ")");
+			}
+			try {
+				textHighlighter.process(sb.toString());
+			} catch (Exception e) {
+				System.out.println(sb.toString());
+				throw e;
+			}
+		}
+
+		Assert.assertEquals("<font color=\"#000000\"></font>)(((())())", textHighlighter.process(")(((())())"));
+		Assert.assertEquals(")", textHighlighter.process(")"));
+		Assert.assertEquals(")()(", textHighlighter.process(")()("));
+	}
+}