diff --git a/app/src/main/java/org/solovyev/android/calculator/Keyboard.java b/app/src/main/java/org/solovyev/android/calculator/Keyboard.java
index 4b37ea06..4adbf7d4 100644
--- a/app/src/main/java/org/solovyev/android/calculator/Keyboard.java
+++ b/app/src/main/java/org/solovyev/android/calculator/Keyboard.java
@@ -26,10 +26,9 @@ import android.content.SharedPreferences;
 import android.support.annotation.NonNull;
 import android.text.TextUtils;
 import android.util.Log;
+
 import com.squareup.otto.Bus;
-import dagger.Lazy;
-import jscl.math.Expression;
-import jscl.math.Generic;
+
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.buttons.CppSpecialButton;
 import org.solovyev.android.calculator.ga.Ga;
@@ -42,6 +41,10 @@ import javax.annotation.Nullable;
 import javax.inject.Inject;
 import javax.inject.Singleton;
 
+import dagger.Lazy;
+import jscl.math.Expression;
+import jscl.math.Generic;
+
 @Singleton
 public class Keyboard implements SharedPreferences.OnSharedPreferenceChangeListener {
 
@@ -69,17 +72,23 @@ public class Keyboard implements SharedPreferences.OnSharedPreferenceChangeListe
     @Inject
     ActivityLauncher launcher;
     private boolean vibrateOnKeypress;
+    private boolean highContrast;
 
     @Inject
     public Keyboard(@Nonnull SharedPreferences preferences) {
         preferences.registerOnSharedPreferenceChangeListener(this);
         vibrateOnKeypress = Preferences.Gui.vibrateOnKeypress.getPreference(preferences);
+        highContrast = Preferences.Gui.highContrast.getPreference(preferences);
     }
 
     public boolean isVibrateOnKeypress() {
         return vibrateOnKeypress;
     }
 
+    public boolean isHighContrast() {
+        return highContrast;
+    }
+
     public boolean buttonPressed(@Nullable String text) {
         if (TextUtils.isEmpty(text)) {
             return false;
@@ -292,6 +301,8 @@ public class Keyboard implements SharedPreferences.OnSharedPreferenceChangeListe
     public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
         if (Preferences.Gui.vibrateOnKeypress.isSameKey(key)) {
             vibrateOnKeypress = Preferences.Gui.vibrateOnKeypress.getPreference(preferences);
+        } else if (Preferences.Gui.highContrast.isSameKey(key)) {
+            highContrast = Preferences.Gui.highContrast.getPreference(preferences);
         }
     }
 }
diff --git a/app/src/main/java/org/solovyev/android/calculator/Preferences.java b/app/src/main/java/org/solovyev/android/calculator/Preferences.java
index e2966ae5..b9549f09 100644
--- a/app/src/main/java/org/solovyev/android/calculator/Preferences.java
+++ b/app/src/main/java/org/solovyev/android/calculator/Preferences.java
@@ -47,6 +47,7 @@ import org.solovyev.android.prefs.*;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+
 import java.util.EnumMap;
 import java.util.Map;
 
@@ -54,7 +55,7 @@ import static org.solovyev.android.prefs.IntegerPreference.DEF_VALUE;
 
 public final class Preferences {
 
-    private static final Preference<Integer> version = IntegerPreference.of("version", 2);
+    private static final Preference<Integer> version = IntegerPreference.of("version", 3);
 
     private Preferences() {
         throw new AssertionError();
@@ -86,6 +87,11 @@ public final class Preferences {
             }
             version.putDefault(editor);
             editor.apply();
+        } else if (currentVersion == 2) {
+            final SharedPreferences.Editor editor = preferences.edit();
+            Gui.highContrast.tryPutDefault(preferences, editor);
+            version.putDefault(editor);
+            editor.apply();
         }
     }
 
@@ -112,6 +118,7 @@ public final class Preferences {
         Gui.rotateScreen.tryPutDefault(preferences, editor);
         Gui.keepScreenOn.tryPutDefault(preferences, editor);
         Gui.language.tryPutDefault(preferences, editor);
+        Gui.highContrast.tryPutDefault(preferences, editor);
 
         Calculations.calculateOnFly.tryPutDefault(preferences, editor);
 
@@ -250,6 +257,7 @@ public final class Preferences {
         public static final Preference<Boolean> useBackAsPrevious = BooleanPreference.of("gui.useBackAsPrevious", false);
         public static final Preference<Boolean> rotateScreen = BooleanPreference.of("gui.rotateScreen", true);
         public static final Preference<Boolean> keepScreenOn = BooleanPreference.of("gui.keepScreenOn", true);
+        public static final Preference<Boolean> highContrast = BooleanPreference.of("gui.highContrast", false);
         public static final Preference<Boolean> vibrateOnKeypress = BooleanPreference.of("gui.vibrateOnKeypress", true);
 
         @Nonnull
diff --git a/app/src/main/java/org/solovyev/android/calculator/keyboard/BaseKeyboardUi.java b/app/src/main/java/org/solovyev/android/calculator/keyboard/BaseKeyboardUi.java
index ee7c45fd..98799cf4 100644
--- a/app/src/main/java/org/solovyev/android/calculator/keyboard/BaseKeyboardUi.java
+++ b/app/src/main/java/org/solovyev/android/calculator/keyboard/BaseKeyboardUi.java
@@ -143,6 +143,7 @@ public abstract class BaseKeyboardUi implements SharedPreferences.OnSharedPrefer
         }
         dragButtons.add(button);
         button.setVibrateOnDrag(keyboard.isVibrateOnKeypress());
+        button.setHighContrast(keyboard.isHighContrast());
         prepareButton((View) button);
         button.setOnDragListener(listener);
         button.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize);
@@ -187,6 +188,11 @@ public abstract class BaseKeyboardUi implements SharedPreferences.OnSharedPrefer
             for (DragView dragButton : dragButtons) {
                 dragButton.setVibrateOnDrag(vibrate);
             }
+        } else if (Preferences.Gui.highContrast.isSameKey(key)) {
+            final boolean highContrast = Preferences.Gui.highContrast.getPreference(preferences);
+            for (DragView dragButton : dragButtons) {
+                dragButton.setHighContrast(highContrast);
+            }
         }
     }
 
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragButton.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragButton.java
index 127a809c..3d44f3e2 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragButton.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragButton.java
@@ -10,10 +10,16 @@ import android.util.AttributeSet;
 
 import javax.annotation.Nonnull;
 
+import static android.graphics.Color.BLACK;
+import static android.util.TypedValue.COMPLEX_UNIT_DIP;
+import static android.util.TypedValue.applyDimension;
+import static org.solovyev.android.views.dragbutton.DirectionTextView.SHADOW_RADIUS_DPS;
+
 public class DirectionDragButton extends DragButton implements DirectionDragView {
     private final DirectionTextView textView = new DirectionTextView();
     @NonNull
     private final TextPaint baseTextPaint = new TextPaint();
+    private boolean highContrast;
 
     public DirectionDragButton(Context context) {
         super(context);
@@ -86,4 +92,18 @@ public class DirectionDragButton extends DragButton implements DirectionDragView
             getText(direction).setAlpha(alpha);
         }
     }
+
+    @Override
+    public void setHighContrast(boolean highContrast) {
+        if(this.highContrast == highContrast) {
+            return;
+        }
+        this.highContrast = highContrast;
+        this.textView.setHighContrast(highContrast);
+        if (highContrast) {
+            setShadowLayer(applyDimension(COMPLEX_UNIT_DIP, SHADOW_RADIUS_DPS, getResources().getDisplayMetrics()), 0, 0, BLACK);
+        } else {
+            setShadowLayer(0, 0, 0, BLACK);
+        }
+    }
 }
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragImageButton.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragImageButton.java
index 9cdc759b..9b882723 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragImageButton.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionDragImageButton.java
@@ -69,4 +69,8 @@ public class DirectionDragImageButton extends DragImageButton implements Directi
     public float getTextSize() {
         return baseTextPaint.getTextSize();
     }
+
+    @Override
+    public void setHighContrast(boolean highContrast) {
+    }
 }
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionTextView.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionTextView.java
index d401d2d5..f268318c 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionTextView.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DirectionTextView.java
@@ -2,7 +2,11 @@ package org.solovyev.android.views.dragbutton;
 
 import android.content.Context;
 import android.content.res.TypedArray;
-import android.graphics.*;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.PointF;
+import android.graphics.Rect;
+import android.graphics.Typeface;
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.text.TextPaint;
@@ -10,17 +14,24 @@ import android.text.TextUtils;
 import android.util.AttributeSet;
 import android.view.View;
 import android.widget.TextView;
+
 import com.google.common.base.Strings;
+
 import org.solovyev.android.Check;
 import org.solovyev.android.calculator.R;
 
 import java.util.EnumMap;
 import java.util.Map;
 
+import static android.graphics.Color.BLACK;
+import static android.util.TypedValue.COMPLEX_UNIT_DIP;
+import static android.util.TypedValue.applyDimension;
+
 public class DirectionTextView {
 
     public static final float DEF_ALPHA = 0.4f;
     public static final float DEF_SCALE = 0.4f;
+    public static final float SHADOW_RADIUS_DPS = 2;
 
     @NonNull
     private final Map<DragDirection, Text> texts = new EnumMap<>(DragDirection.class);
@@ -78,6 +89,12 @@ public class DirectionTextView {
         return texts.get(direction);
     }
 
+    public void setHighContrast(boolean highContrast) {
+        for (Text text : texts.values()) {
+            text.setHighContrast(highContrast);
+        }
+    }
+
     public static class Text {
         public final Rect bounds = new Rect();
         @NonNull
@@ -96,6 +113,7 @@ public class DirectionTextView {
         private int color;
         private float alpha;
         private boolean visible = true;
+        private boolean highContrast;
         private int padding;
 
         public Text(@NonNull DragDirection direction, @NonNull View view, float minTextSize) {
@@ -138,9 +156,18 @@ public class DirectionTextView {
             // set real text size value
             paint.setTextSize(Math.max(base.getTextSize() * scale, minTextSize));
 
+            initPaintShadow();
             invalidate(true);
         }
 
+        private void initPaintShadow() {
+            if (highContrast) {
+                paint.setShadowLayer(applyDimension(COMPLEX_UNIT_DIP, SHADOW_RADIUS_DPS, view.getResources().getDisplayMetrics()), 0, 0, BLACK);
+            } else {
+                paint.setShadowLayer(0, 0, 0, BLACK);
+            }
+        }
+
         private int intAlpha() {
             return (int) (255 * alpha);
         }
@@ -161,6 +188,15 @@ public class DirectionTextView {
             setColor(color, alpha);
         }
 
+        public void setHighContrast(boolean highContrast) {
+            if (this.highContrast == highContrast) {
+                return;
+            }
+            this.highContrast = highContrast;
+            initPaintShadow();
+            invalidate(false);
+        }
+
         public void setColor(int color, float alpha) {
             if (this.color == color && this.alpha == alpha) {
                 return;
@@ -187,6 +223,10 @@ public class DirectionTextView {
             if (offset.x == 0 && offset.y == 0) {
                 calculatePosition();
             }
+            if (highContrast) {
+                paint.setColor(Color.WHITE);
+                paint.setAlpha(255);
+            }
             final int width = view.getWidth();
             final int height = view.getHeight();
             switch (direction) {
@@ -203,6 +243,10 @@ public class DirectionTextView {
                     canvas.drawText(value, width + offset.x, height / 2 + offset.y, paint);
                     break;
             }
+            if (highContrast) {
+                paint.setColor(color);
+                paint.setAlpha(intAlpha());
+            }
         }
 
         private void calculatePosition() {
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DragButton.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DragButton.java
index d0d8049b..ddb7e828 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DragButton.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DragButton.java
@@ -9,7 +9,7 @@ import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.widget.Button;
 
-public class DragButton extends Button implements DragView {
+public abstract class DragButton extends Button implements DragView {
     @NonNull
     private final DragGestureDetector dragDetector = new DragGestureDetector(this);
 
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DragImageButton.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DragImageButton.java
index 9413ce51..95f6f7dd 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DragImageButton.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DragImageButton.java
@@ -9,7 +9,7 @@ import android.util.AttributeSet;
 import android.view.MotionEvent;
 import android.widget.ImageButton;
 
-public class DragImageButton extends ImageButton implements DragView {
+public abstract class DragImageButton extends ImageButton implements DragView {
     @NonNull
     private final DragGestureDetector dragDetector = new DragGestureDetector(this);
 
diff --git a/app/src/main/java/org/solovyev/android/views/dragbutton/DragView.java b/app/src/main/java/org/solovyev/android/views/dragbutton/DragView.java
index 06c3813a..d37fbbc5 100644
--- a/app/src/main/java/org/solovyev/android/views/dragbutton/DragView.java
+++ b/app/src/main/java/org/solovyev/android/views/dragbutton/DragView.java
@@ -6,4 +6,5 @@ public interface DragView {
     int getId();
     void setOnDragListener(@Nullable DragListener listener);
     void setVibrateOnDrag(boolean vibrateOnDrag);
+    void setHighContrast(boolean highContrast);
 }
diff --git a/app/src/main/res/xml/preferences_appearance.xml b/app/src/main/res/xml/preferences_appearance.xml
index b5781f59..6870eddb 100644
--- a/app/src/main/res/xml/preferences_appearance.xml
+++ b/app/src/main/res/xml/preferences_appearance.xml
@@ -38,6 +38,10 @@
         a:key="gui.theme"
         a:title="@string/cpp_theme" />
 
+    <android.preference.CheckBoxPreference
+        a:key="gui.highContrast"
+        a:title="High contrast" />
+
     <android.preference.CheckBoxPreference
         a:defaultValue="true"
         a:key="gui.rotateScreen"