Cannot add dependencies to gdx-pd in my LibGDX project

Question

everyone! I am trying to add dependencies to gdx-pd in build.gradle, but when I try to synk the project, I am getting this error:

Caused by: groovy.lang.MissingPropertyException: Could not get unknown property 'pdVersion' for object of type org.gradle.api.internal.artifacts.dsl.dependencies.DefaultDependencyHandler.

This is how my Gradle file looks like:

buildscript {


repositories {
    mavenLocal()
    mavenCentral()
    maven { url "https://plugins.gradle.org/m2/" }
    maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
    jcenter()
    google()
}
dependencies {
    classpath 'com.android.tools.build:gradle:3.6.1'


}

}

allprojects {

version = '1.0'
ext {
    appName = "audio-demo"
    gdxVersion = '1.9.10'
    roboVMVersion = '2.3.7'
    box2DLightsVersion = '1.4'
    ashleyVersion = '1.7.0'
    aiVersion = '1.8.0'
}

repositories {
    mavenLocal()
    mavenCentral()
    jcenter()
    google()
    maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
    maven { url "https://oss.sonatype.org/content/repositories/releases/" }
}

}

project(":desktop") { apply plugin: "java-library"

dependencies {
    implementation project(":core")
    api "com.badlogicgames.gdx:gdx-backend-lwjgl:$gdxVersion"
    api "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-desktop"
    api "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-desktop"
    api "com.badlogicgames.gdx:gdx-tools:$gdxVersion"
    api "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-desktop"
    api "net.mgsx.gdx:gdx-pd-platform:$pdVersion:desktop"
    api "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-desktop"
}

}

project(":android") { apply plugin: "android"

configurations { natives }

dependencies {
    implementation project(":core")
    api "com.badlogicgames.gdx:gdx-backend-android:$gdxVersion"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi-v7a"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-arm64-v8a"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86"
    natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86_64"
    api "com.badlogicgames.gdx:gdx-box2d:$gdxVersion"
    natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi"
    natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi-v7a"
    natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-arm64-v8a"
    natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-x86"
    natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-x86_64"
    api "com.badlogicgames.gdx:gdx-freetype:$gdxVersion"
    natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi"
    natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi-v7a"
    natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-arm64-v8a"
    natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-x86"
    natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-x86_64"
    api "net.mgsx.gdx:gdx-pd-backend-android:$pdVersion"
    natives "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-armeabi"
    natives "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-armeabi-v7a"
    natives "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-arm64-v8a"
    natives "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-x86"
    natives "net.mgsx.gdx:gdx-pd-platform:$pdVersion:natives-x86_64"
}

}

project(":core") { apply plugin: "java-library"

dependencies {
    api "com.badlogicgames.gdx:gdx:$gdxVersion"
    api "com.badlogicgames.gdx:gdx-box2d:$gdxVersion"
    api "com.badlogicgames.gdx:gdx-freetype:$gdxVersion"
    api "net.mgsx.gdx:gdx-pd:$pdVersion"
}

}

If I try to specify $pdVersion like this:

ext {
    ...
    pdVersion = '0.7.0'
}

I am getting another error:

ERROR: Failed to resolve: net.mgsx.gdx:gdx-pd:0.7.0 Show in Project Structure dialog Affected Modules: core ERROR: Failed to resolve: net.mgsx.gdx:gdx-pd:0.7.0 Show in Project Structure dialog Affected Modules: android

What am I doing wrong? Thank you in advance!