package com.badlogic.invaders.client;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.backends.gwt.GwtApplication;
import com.badlogic.gdx.backends.gwt.GwtApplicationConfiguration;
import com.badlogic.invaders.Invaders;

public class HtmlLauncher extends GwtApplication {

        @Override
        public GwtApplicationConfiguration getConfig () {
                return new GwtApplicationConfiguration(480, 320);
        }

        @Override
        public ApplicationListener getApplicationListener () {
                return new Invaders();
        }
}
package com.badlogic.invaders.client;

import com.badlogic.gdx.ApplicationListener;
import com.badlogic.gdx.backends.gwt.GwtApplication;
import com.badlogic.gdx.backends.gwt.GwtApplicationConfiguration;
import com.badlogic.invaders.Invaders;

public class HtmlLauncher extends GwtApplication {

        @Override
        public GwtApplicationConfiguration getConfig () {
                return new GwtApplicationConfiguration(480, 320);
        }

        @Override
        public ApplicationListener createApplicationListener () {
                return new Invaders();
        }
}

Update HtmlLauncher.java