We've added more sounds, not just ambient sound. We have added new models such as the arch the player is sitting on and the projectiles the aliens throw. Now destroying object is a bit smoother, we've tried changing some effects. We've added antialiasing. We've added keyboard input (in case you don't want to play using the mouse). Another effect we've added is the big spaceship that captures the castle at the end of the game. We've added something I like to call "Super aliens", They are just aliens that take ofer the castle (They don't change the gameplay). They are removed by the people fixing the castle during the day.
That's about it, thanks for reading!