diff --git a/.idea/compiler.xml b/.idea/compiler.xml
deleted file mode 100644
index 96cc43e..0000000
--- a/.idea/compiler.xml
+++ /dev/null
@@ -1,22 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="CompilerConfiguration">
-    <resourceExtensions />
-    <wildcardResourcePatterns>
-      <entry name="!?*.java" />
-      <entry name="!?*.form" />
-      <entry name="!?*.class" />
-      <entry name="!?*.groovy" />
-      <entry name="!?*.scala" />
-      <entry name="!?*.flex" />
-      <entry name="!?*.kt" />
-      <entry name="!?*.clj" />
-      <entry name="!?*.aj" />
-    </wildcardResourcePatterns>
-    <annotationProcessing>
-      <profile default="true" name="Default" enabled="false">
-        <processorPath useClasspath="true" />
-      </profile>
-    </annotationProcessing>
-  </component>
-</project>
\ No newline at end of file
diff --git a/.idea/copyright/profiles_settings.xml b/.idea/copyright/profiles_settings.xml
deleted file mode 100644
index e7bedf3..0000000
--- a/.idea/copyright/profiles_settings.xml
+++ /dev/null
@@ -1,3 +0,0 @@
-<component name="CopyrightManager">
-  <settings default="" />
-</component>
\ No newline at end of file
diff --git a/.idea/gradle.xml b/.idea/gradle.xml
deleted file mode 100644
index 7ac24c7..0000000
--- a/.idea/gradle.xml
+++ /dev/null
@@ -1,18 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="GradleSettings">
-    <option name="linkedExternalProjectsSettings">
-      <GradleProjectSettings>
-        <option name="distributionType" value="DEFAULT_WRAPPED" />
-        <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="modules">
-          <set>
-            <option value="$PROJECT_DIR$" />
-            <option value="$PROJECT_DIR$/app" />
-          </set>
-        </option>
-        <option name="resolveModulePerSourceSet" value="false" />
-      </GradleProjectSettings>
-    </option>
-  </component>
-</project>
\ No newline at end of file
diff --git a/.idea/misc.xml b/.idea/misc.xml
deleted file mode 100644
index 50282c1..0000000
--- a/.idea/misc.xml
+++ /dev/null
@@ -1,88 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="EntryPointsManager">
-    <entry_points version="2.0" />
-  </component>
-  <component name="NullableNotNullManager">
-    <option name="myDefaultNullable" value="android.support.annotation.Nullable" />
-    <option name="myDefaultNotNull" value="android.support.annotation.NonNull" />
-    <option name="myNullables">
-      <value>
-        <list size="4">
-          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.Nullable" />
-          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nullable" />
-          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.Nullable" />
-          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.Nullable" />
-        </list>
-      </value>
-    </option>
-    <option name="myNotNulls">
-      <value>
-        <list size="4">
-          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.NotNull" />
-          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nonnull" />
-          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.NonNull" />
-          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.NonNull" />
-        </list>
-      </value>
-    </option>
-  </component>
-  <component name="ProjectInspectionProfilesVisibleTreeState">
-    <entry key="Project Default">
-      <profile-state>
-        <expanded-state>
-          <State>
-            <id />
-          </State>
-        </expanded-state>
-        <selected-state>
-          <State>
-            <id>Android</id>
-          </State>
-        </selected-state>
-      </profile-state>
-    </entry>
-  </component>
-  <component name="ProjectLevelVcsManager" settingsEditedManually="false">
-    <OptionsSetting value="true" id="Add" />
-    <OptionsSetting value="true" id="Remove" />
-    <OptionsSetting value="true" id="Checkout" />
-    <OptionsSetting value="true" id="Update" />
-    <OptionsSetting value="true" id="Status" />
-    <OptionsSetting value="true" id="Edit" />
-    <ConfirmationsSetting value="0" id="Add" />
-    <ConfirmationsSetting value="0" id="Remove" />
-  </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" default="true" assert-keyword="true" jdk-15="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
-    <output url="file://$PROJECT_DIR$/build/classes" />
-  </component>
-  <component name="ProjectType">
-    <option name="id" value="Android" />
-  </component>
-  <component name="masterDetails">
-    <states>
-      <state key="Copyright.UI">
-        <settings>
-          <splitter-proportions>
-            <option name="proportions">
-              <list>
-                <option value="0.2" />
-              </list>
-            </option>
-          </splitter-proportions>
-        </settings>
-      </state>
-      <state key="ScopeChooserConfigurable.UI">
-        <settings>
-          <splitter-proportions>
-            <option name="proportions">
-              <list>
-                <option value="0.2" />
-              </list>
-            </option>
-          </splitter-proportions>
-        </settings>
-      </state>
-    </states>
-  </component>
-</project>
\ No newline at end of file
diff --git a/.idea/modules.xml b/.idea/modules.xml
deleted file mode 100644
index 3a3eea2..0000000
--- a/.idea/modules.xml
+++ /dev/null
@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="ProjectModuleManager">
-    <modules>
-      <module fileurl="file://$PROJECT_DIR$/app/app.iml" filepath="$PROJECT_DIR$/app/app.iml" />
-      <module fileurl="file://$PROJECT_DIR$/privacy-friendly-sudoku.iml" filepath="$PROJECT_DIR$/privacy-friendly-sudoku.iml" />
-    </modules>
-  </component>
-</project>
\ No newline at end of file
diff --git a/.idea/runConfigurations.xml b/.idea/runConfigurations.xml
deleted file mode 100644
index 7f68460..0000000
--- a/.idea/runConfigurations.xml
+++ /dev/null
@@ -1,12 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="RunConfigurationProducerService">
-    <option name="ignoredProducers">
-      <set>
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.AllInPackageGradleConfigurationProducer" />
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestClassGradleConfigurationProducer" />
-        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestMethodGradleConfigurationProducer" />
-      </set>
-    </option>
-  </component>
-</project>
\ No newline at end of file