public class MainScreen extends ApplicationAdapter implements InputProcessor {
OrthographicCamera camera;
Viewport viewport;
Vector3 worldCoordinates = new Vector3();
Shape shape, background;
public ShapeRenderer sr;

@Override
public void create() {
    worldCoordinates = new Vector3();
    camera = new OrthographicCamera(800,480);
    camera.position.set(camera.viewportWidth / 2, camera.viewportHeight / 2, 0);
    viewport = new FitViewport(800, 480, camera);
    viewport.apply();
    sr = new ShapeRenderer();
    shape = new Shape(this, 20, 20, 0, 0);
    background = new Shape(this, 800, 480, 0, 0, Color.WHITE);
    Gdx.input.setInputProcessor(this);
}

@Override
public void resize(int width, int height) {
    viewport.update(width, height);
    camera.position.set(camera.viewportWidth / 2, camera.viewportHeight / 2, 0);
}

@Override
public void dispose() {

}

@Override
public void pause() {

}

@Override
public void resume() {

}

@Override
public void render() {
    camera.update();

    Gdx.gl.glClearColor(0, 0.1f, 0.1f, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    background.render();
    sr.setProjectionMatrix(camera.combined);

    shape.posX[0] = (int) worldCoordinates.x - shape.sizeX[0] / 2;
    shape.posY[0] = (int) worldCoordinates.y - shape.sizeY[0] / 2;

    shape.render();
}

@Override
public boolean mouseMoved(int screenX, int screenY) {
    worldCoordinates = camera.unproject(new Vector3(screenX, screenY, 0));
    return true;
}

@Override
public boolean keyDown(int keycode) {
    throw new UnsupportedOperationException("Not supported yet.");
}

@Override
public boolean keyUp(int keycode) {
    throw new UnsupportedOperationException("Not supported yet.");
}

@Override
public boolean keyTyped(char character) {
    throw new UnsupportedOperationException("Not supported yet.");
}

@Override
public boolean touchDown(int screenX, int screenY, int pointer, int button) {
    return true;
}

@Override
public boolean touchUp(int screenX, int screenY, int pointer, int button) {
    return true;
}

@Override
public boolean touchDragged(int screenX, int screenY, int pointer) {
    return false;
}

@Override
public boolean scrolled(int amount) {
    throw new UnsupportedOperationException("Not supported yet.");
}
}

public class Shape extends Element {
public Color background;
ShapeRenderer sr;
public Shape( MainScreen ms, int sizeX, int sizeY, int posX, int posY){
    super(sizeX, sizeY, posX, posY);
    sr=ms.sr;
    sr.setAutoShapeType(true);
    background = new Color();
    background.set(1, 0.533f, 0, 1);
}
public Shape(MainScreen ms, int sizeX, int sizeY, int posX, int posY, Color background){
    super(sizeX, sizeY, posX, posY);
    sr=ms.sr;
    sr.setAutoShapeType(true);
    this.background = background;
}

@Override
public void render(){
    sr.begin(ShapeRenderer.ShapeType.Filled);
    sr.setColor(background);
    sr.rect(posX[0],posY[0],sizeX[0],sizeY[0]);
    sr.end();
}
}

@Override
public boolean mouseMoved(int screenX, int screenY) {
    worldCoordinates = camera.unproject(new Vector3(screenX, screenY, 0));
    return true;
}

worldCoordinates = camera.unproject(new Vector3(screenX, screenY, 0), viewport.getScreenX(), viewport.getScreenY(), viewport.getScreenWidth(), viewport.getScreenHeight());