diff --git a/ant/build.gradle b/ant/build.gradle
index ddb6063f..ed589528 100644
--- a/ant/build.gradle
+++ b/ant/build.gradle
@@ -17,6 +17,7 @@ targetCompatibility = "${target}"
 sourceSets.main {
     java {
         srcDirs = ['src']
+        include '**/*.java'
     }
     resources {
         srcDirs = ['src']
@@ -28,16 +29,16 @@ sourceSets.main {
 }
 
 dependencies {
-    compile project(':base')
-    compile 'com.guardsquare:proguard-core'
-    compile 'org.apache.ant:ant:1.9.7'
+    implementation project(':base')
+    implementation 'com.guardsquare:proguard-core'
+    implementation 'org.apache.ant:ant:1.9.7'
 }
 
 task fatJar(type: ShadowJar) {
     destinationDirectory.set(file("$rootDir/lib"))
     archiveFileName.set('proguard-ant.jar')
     from sourceSets.main.output
-    configurations = [project.configurations.runtime]
+    configurations = [project.configurations.runtimeClasspath]
     manifest {
         attributes(
                 'Manifest-Version': '1.0',
diff --git a/base/build.gradle b/base/build.gradle
index 5102cc8f..49059f11 100644
--- a/base/build.gradle
+++ b/base/build.gradle
@@ -28,8 +28,8 @@ sourceSets.main {
 }
 
 dependencies {
-    compile "com.guardsquare:proguard-core:${proguardCoreVersion}"
-    compile "com.google.code.gson:gson:${gsonVersion}"
+    implementation "com.guardsquare:proguard-core:${proguardCoreVersion}"
+    implementation "com.google.code.gson:gson:${gsonVersion}"
 }
 
 jar.manifest.attributes('Implementation-Version': version)
@@ -38,7 +38,7 @@ task fatJar(type: ShadowJar) {
     destinationDirectory.set(file("$rootDir/lib"))
     archiveFileName.set('proguard.jar')
     from sourceSets.main.output
-    configurations = [project.configurations.runtime]
+    configurations = [project.configurations.runtimeClasspath]
     manifest {
         attributes(
                 'Main-Class': 'proguard.ProGuard',
diff --git a/build.gradle b/build.gradle
index 66edb62a..58bbbb6e 100644
--- a/build.gradle
+++ b/build.gradle
@@ -10,11 +10,6 @@ allprojects {
     version = proguardVersion
 }
 
-wrapper {
-    gradleVersion = '6.8'
-    distributionType = Wrapper.DistributionType.ALL
-}
-
 task buildDocumentation(type: Exec) {
     inputs.dir 'docs/md'
     inputs.file 'docs/mkdocs.yml'
diff --git a/examples/android-plugin/gradle/wrapper/gradle-wrapper.jar b/examples/android-plugin/gradle/wrapper/gradle-wrapper.jar
index 5c2d1cf0..e708b1c0 100644
Binary files a/examples/android-plugin/gradle/wrapper/gradle-wrapper.jar and b/examples/android-plugin/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/examples/android-plugin/gradle/wrapper/gradle-wrapper.properties b/examples/android-plugin/gradle/wrapper/gradle-wrapper.properties
index f4d7b2bf..2a563242 100644
--- a/examples/android-plugin/gradle/wrapper/gradle-wrapper.properties
+++ b/examples/android-plugin/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.4.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.jar b/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.jar
index f3d88b1c..e708b1c0 100644
Binary files a/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.jar and b/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.properties b/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.properties
index 1b16c34a..2a563242 100644
--- a/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.properties
+++ b/examples/gradlekotlindsl/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/examples/gradlekotlindsl/gradlew b/examples/gradlekotlindsl/gradlew
index 2fe81a7d..4f906e0c 100755
--- a/examples/gradlekotlindsl/gradlew
+++ b/examples/gradlekotlindsl/gradlew
@@ -82,6 +82,7 @@ esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
+
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
@@ -129,6 +130,7 @@ fi
 if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
     APP_HOME=`cygpath --path --mixed "$APP_HOME"`
     CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
     JAVACMD=`cygpath --unix "$JAVACMD"`
 
     # We build the pattern for arguments to be converted via cygpath
diff --git a/examples/gradlekotlindsl/gradlew.bat b/examples/gradlekotlindsl/gradlew.bat
index 9618d8d9..107acd32 100644
--- a/examples/gradlekotlindsl/gradlew.bat
+++ b/examples/gradlekotlindsl/gradlew.bat
@@ -29,6 +29,9 @@ if "%DIRNAME%" == "" set DIRNAME=.
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
 @rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
 set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
 
@@ -37,7 +40,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto init
+if "%ERRORLEVEL%" == "0" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -51,7 +54,7 @@ goto fail
 set JAVA_HOME=%JAVA_HOME:"=%
 set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
-if exist "%JAVA_EXE%" goto init
+if exist "%JAVA_EXE%" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
@@ -61,28 +64,14 @@ echo location of your Java installation.
 
 goto fail
 
-:init
-@rem Get command-line arguments, handling Windows variants
-
-if not "%OS%" == "Windows_NT" goto win9xME_args
-
-:win9xME_args
-@rem Slurp the command line arguments.
-set CMD_LINE_ARGS=
-set _SKIP=2
-
-:win9xME_args_slurp
-if "x%~1" == "x" goto execute
-
-set CMD_LINE_ARGS=%*
-
 :execute
 @rem Setup the command line
 
 set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
+
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
 
 :end
 @rem End local scope for the variables with windows NT shell
diff --git a/examples/spring-boot/build.gradle b/examples/spring-boot/build.gradle
index 4b3ee567..5cdb86fb 100644
--- a/examples/spring-boot/build.gradle
+++ b/examples/spring-boot/build.gradle
@@ -60,8 +60,8 @@ task repackage(type: Zip) {
 
     from  "${buildDir}/extracted"
     entryCompression ZipEntryCompression.STORED
-    archiveName "demo-$version-obfuscated.jar"
-    destinationDir(file("${buildDir}/libs"))
+    archiveFileName= "demo-$archiveVersion-obfuscated.jar"
+    destinationDirectory = file("${buildDir}/libs")
 }
 
 task proguard(type: ProGuardTask) {
diff --git a/examples/spring-boot/gradle/wrapper/gradle-wrapper.properties b/examples/spring-boot/gradle/wrapper/gradle-wrapper.properties
index 12d38de6..2a563242 100644
--- a/examples/spring-boot/gradle/wrapper/gradle-wrapper.properties
+++ b/examples/spring-boot/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradle-plugin/build.gradle b/gradle-plugin/build.gradle
index 12920766..1dee1171 100644
--- a/gradle-plugin/build.gradle
+++ b/gradle-plugin/build.gradle
@@ -16,10 +16,14 @@ targetCompatibility = "${target}"
 sourceSets.main {
     java {
         srcDirs = ['src']
+        include '**/*.java'
+        exclude 'META-INF/**'
     }
 
     groovy {
         srcDirs = ['src']
+        include '**/*.groovy'
+        exclude 'META-INF/**'
     }
 
     resources {
@@ -57,11 +61,6 @@ jar {
     metaInf.from 'src/META-INF'
 }
 
-repositories {
-    google()
-    jcenter()
-}
-
 dependencies {
     implementation project(':base')
     implementation 'com.guardsquare:proguard-core'
@@ -70,7 +69,7 @@ dependencies {
     implementation localGroovy()
     testImplementation gradleTestKit()
     testImplementation 'junit:junit:4.13.1'
-    testImplementation "org.spockframework:spock-core:1.1-groovy-2.4@jar"
+    testImplementation "org.spockframework:spock-core:1.3-groovy-2.5"
     testImplementation "commons-io:commons-io:2.8.0"
 }
 
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 80cf08e7..2a563242 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.8-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.8.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gui/build.gradle b/gui/build.gradle
index db0fc8d6..c642dfb5 100644
--- a/gui/build.gradle
+++ b/gui/build.gradle
@@ -17,6 +17,7 @@ targetCompatibility = "${target}"
 sourceSets.main {
     java {
         srcDirs = ['src']
+        include '**/*.java'
     }
     resources {
         srcDirs = ['src']
@@ -28,16 +29,16 @@ sourceSets.main {
 }
 
 dependencies {
-    compile project(':base')
-    compile 'com.guardsquare:proguard-core'
-    compile project(':retrace')
+    implementation project(':base')
+    implementation 'com.guardsquare:proguard-core'
+    implementation project(':retrace')
 }
 
 task fatJar(type: ShadowJar) {
     destinationDirectory.set(file("$rootDir/lib"))
     archiveFileName.set('proguardgui.jar')
     from sourceSets.main.output
-    configurations = [project.configurations.runtime]
+    configurations = [project.configurations.runtimeClasspath]
     manifest {
         attributes(
                 'Manifest-Version': '1.0',
diff --git a/retrace/build.gradle b/retrace/build.gradle
index 10783bbe..2a4fbf5e 100644
--- a/retrace/build.gradle
+++ b/retrace/build.gradle
@@ -28,15 +28,15 @@ sourceSets.main {
 }
 
 dependencies {
-    compile project(':base')
-    compile 'com.guardsquare:proguard-core'
+    implementation project(':base')
+    implementation 'com.guardsquare:proguard-core'
 }
 
 task fatJar(type: ShadowJar) {
     destinationDirectory.set(file("$rootDir/lib"))
     archiveFileName.set('retrace.jar')
     from sourceSets.main.output
-    configurations = [project.configurations.runtime]
+    configurations = [project.configurations.runtimeClasspath]
     manifest {
         attributes(
                 'Manifest-Version': '1.0',
@@ -44,4 +44,4 @@ task fatJar(type: ShadowJar) {
     }
 }
 
-assemble.dependsOn fatJar
\ No newline at end of file
+assemble.dependsOn fatJar