When the original game came out, it introduced gamers to a weird, wild world filled with extradimensional entities, reality changing powers, government cover-ups, and a strong female lead. The Foundation keeps this trend going, picking up right where the main game leaves off. Although the base game feels like a complete experience on its own, The Foundation still manages to seamlessly incorporate itself into the overall adventure. It does exactly what a good expansion should do by naturally adding on to what the fans are already familiar with, both in terms of story and in features, while setting the stage for the future.
Over the course of the story, The Foundation gives players a couple of new powers to play around with, giving Jesse the ability to create or destroy crystal structures in specific areas. While these are useful and fun, they're also limited to specific situations and locations. These abilities are used more as a way to get from Point A to Point B in the expansion content than anything, and they don't add anything to the base game. In fact, from a strictly gameplay perspective, The Foundation is relatively self-contained. Players explore the lower levels of the Bureau, backtracking and revisiting different areas there as they search out the four nodes of the damaged Nail. It's more closed in than the main game, but it's also meant to be a much smaller, episodic adventure. Still, from a storyline point of view, The Foundation adds some hefty twists and turns to the game's lore, and does a fantastic job of leaving fans of the game eager to discover what happens next.