Expecting Super Smash Bros. Ultimate to be a good party game goes without saying: it’s essentially the same Smash Bros. that fans have loved for years, just taken to the natural limit. But when I recently had the chance to play a few hours of Nintendo’s character fighter, it was Ultimate’s single-player offering that stood out to me the most. The recently announced Spirits mode is much more important than it first seems.

After the Wii U version of Smash skipped out on a single-player adventure, Spirits mode returns to fill that gap. It’s not quite a linear story mode in the same way as Super Smash Bros. Brawl’s Subspace Emissary mode was — although there are cutscenes and an overarching storyline — but it fills a similar role.

In Spirits mode, you’re presented with a vast overworld map that’s dotted with different characters that represent the different “Spirit” fighters, which are versions of Smash characters that have been inhabited by the spirit of another video game persona, with their abilities and stage tweaked to match.

For example, a Spirit battle against a fighter inhabited by the flying dragon pokémon Rayquaza had me battle against Smash Bros. fighter Ridley, who was scaled up larger and colored green on a stage that had additional rushing winds. In another fight, I battled a swarm of yellow Kirbys, representing the Metroid franchise’s X Parasites. Each Spirit battle is themed to a specific character, and Nintendo has done some clever work in creatively bending the roster of Smash characters and stages to fit the different themes.

Defeat a spirit, and they’re added to your collection where you can use them to imbue your own fighters with special abilities. Spirits also have levels, and in a Pokémon-like system, you can train and upgrade your Spirits to make them even stronger. Spirits have different types that are more or less effective against others, and there’s a whole roster of secondary spirits that can grant additional effects (like, say, decreasing movement speed but increasing damage), which adds a whole level of strategic depth.

To go back to that Rayquaza fight, it wasn’t until I equipped a Spirit that negated the effects of strong wind that I stood a chance at victory. If it sounds a little confusing, that’s because it is — at least at first. But there’s plenty of helpful information and a handy “autopick” button that will select a recommended loadout for the specific challenge of your unlocked spirits if you prefer to stick to fighting.

In the main Spirit mode, you’ll battle through a gauntlet of Spirit fights, unlocking more challenges and more of the map as you play through the story. There’s also a Spirit Board mode, where you’ll be able to select a constantly rotating board of challenges to get new spirits.

The key here is that there’s a huge amount of variety in the challenges, and none of them are very long. You go in, fight your opponent, and get your rewards. And between the Spirit adventure mode and the board, there’s always something interesting to do. And unlike, say, Subspace Emissary, which awkwardly grafted Smash gameplay onto a platforming and boss fight mode, Spirits is still, at its core, the same Smash Bros. experience you know and love. If you’re great at Smash already, Spirits will take advantage of those skills; if not, it’ll eventually help you get better.

It’s the sort of bite-sized content that evokes some of the Switch’s other blockbuster hits. Breath of the Wild may have been the biggest Zelda game ever, but its smaller shrines and shorter, quicker mini-dungeons are the kind that you could easily knock out on a subway trip. The same goes for Super Mario Odyssey’s hundreds of moons, which are the perfect sort of challenge to run during a commercial break on a lazy afternoon spent watching football.

The smaller Spirit battles from Ultimate fill that same sort of gap that takes advantage of the Switch’s best feature: the ability to take it anywhere and play it anytime. Sure, the focus is still very firmly on those iconic multiplayer battles, which are bigger, better, and more bombastic than ever before. And I’m sure there will be plenty of people who will take advantage of the Switch’s detachable controllers to do just that, duking out Final Destination-style duels anywhere.

But when I think about how I’ve mostly used my Switch over the past year and a half, it’s been far more time spent on a plane or a train or a few minutes before bed than at giant parties. It’s good to see Nintendo acknowledging that with features like Spirits mode, even in a game like Smash.