One of many spin-offs to come out of Nintendo's Pokémon phenomenon, the Rumble series takes toy versions of Game Freak's famous monsters and throws them into simple, action-packed beat-'em-ups. The 3DS has already played host to Pokémon Rumble Blast, but following in the free-to-play footsteps of the recently released Pokémon Shuffle, the latest title in the series - Pokémon Rumble World - is a free-to-download eShop exclusive. While that low price includes optional microtransactions, this is no Team Rocket scam - Rumble World's pricing model is pleasantly palatable, and with fun gameplay and connectivity features, this freebie deserves a download on any Pokémon fan's system.

As with every game in the Rumble series, Rumble World tempers its beat-'em-up gameplay through a toyland conceit: your Mii is transported into the Kingdom of Toys, where toy Pokémon roam wild and free. The King of the realm, sadly, has only a single Pokémon to his name and - after outfitting you with his personal Pikachu and a hot air balloon for travel - tasks you with expanding his collection.

The basic gameplay remains largely unchanged from Rumble's WiiWare beginnings: playing as the toy Pokémon of your choice, you'll move through simple, semi-randomized paths, encountering sizeable same-species swarms of Pokémon along the way, which you'll defeat with simple "mash 'A'"-style combat. After clearing a few different rooms, you'll come to an arena holding the boss - a larger, more powerful Pokémon accompanied by an endless supply of minions.

Sometimes, instead of disappearing in a flash of light, the Pokémon you defeat will turn into tinier toy version of themselves, which can be picked up and added to your team. You can switch between Pokémon on the fly with a quick press of the X button, and you'll want to switch often as you encounter different foes - the series' trademark Type advantages come into play here, and planning your strategy around 'Super Effective' moves is a surefire way to clear out packs of enemy Pokémon.

Beyond Types, the individual Pokémon makes a difference too - each monster you find will have different power ratings and different moves, so you might find one Treecko who fights with 'Tackle', another who uses 'Absorb', and another that whips out 'Razor Leaf'. Some Pokémon even come with special Traits that bestow bonuses, like our Healthy Horsea, who restores HP naturally, or our Turbo Weepinbell, who essentially emulates a turbo button for rapid-fire attacks. Between Traits, moveset differences, and the fact that all 700+ currently known Pokémon are present in the game, "catching 'em all" might be a stretch - but it's always exciting to see what you come back with.

Catching new Pokémon does feel like the main draw of the game, but the combat - while very simple - is surprisingly fun too. It's definitely repetitive, and button mashing will certainly carry you through most battles, but there are some nuances that make battle more satisfying than you might think. Some attacks (like 'Tackle') hit straight ahead, for instance, while others (like 'Razor Leaf') carve out a hitbox that circles around your Pokémon, and some (like 'Twister') only start dealing damage a few feet away from your 'mon - great for keeping foes at bay, but useless point blank. You'll also find defensive moves, as well as buffs and debuffs that do everything from reduce damage or inflict status conditions to change a Pokémon's Type.

So far, Rumble World sounds very similar to its 3DS predecessor, Rumble Blast, but it differs substantially in how it's structured. Rather than spread out on a world map or arranged in a linear progression, the levels in Rumble World are accessed via special Hot Air Balloons - and that's where the game's free-to-play system comes in.

Balloons - there are eighteen in total - whisk you away to different themed areas, with several sub-levels available to explore from each Balloon. If you hop aboard the Sapphire Balloon, for instance, you'll be able to land in one of four stages - selected semi-randomly via a roulette system - which feature mostly Generation III Pokémon from Ruby and Sapphire. The Dew Balloon, meanwhile, takes you to lands teeming with Water-type Pokémon, while the Origin Balloon drops you off in the stomping grounds of the original Kanto 150. All Balloons need air, however, and after you use one, it will take some real-world time to recharge before you can hop in again - anywhere from a few minutes to a few hours, depending on the Balloon.

At the outset of your adventure, you'll get a starter Balloon for free, but after that you'll need to buy more with Poké Diamonds. This is Rumble World's in-game currency of choice, and though they're purchasable with real-world money - at the rate of $0.69/€0.69/£0.69 for 50 Diamonds, with substantial bulk discounts for higher quantities - you'll also pick up plenty just by playing the game. They're used not only to buy new Balloons, but also to grab certain items and upgrades, as well as instantly reinflate a Balloon if you don't feel like waiting.

Happily, however, Rumble World's timer-based model feels remarkably unrestrictive - we never once felt compelled to pump up a Balloon with Poké Diamonds, and we weren't left waiting around because of it. For starters, there's a whole suite of Challenge stages at the castle that can be played without using a Balloon at all. These missions involve specific requests from the King, such as beating a boss, protecting a Mii, or winning a Battle Royale, and completing them will earn you Poké Diamonds. Each Challenge also comes with smaller subgoals - like using super effective attacks, clearing the mission in a certain time, or racking up a high combo - which will earn you even more Diamonds as you check them off. Though you can't capture any Pokémon in the Challenges, you can play each mission as many times as you like - and try them on Hard mode for even more Diamonds after clearing them once.

As with Pokémon Shuffle, we'd argue that there's no real need to throw any real money at Rumble World; it doesn't take long to build up a respectable fleet of Balloons, and with the Challenges playable and replayable at any time, there's always something fun to do while you're waiting.

That said, players who do feel like splashing out on Poké Diamonds can do so without worry of falling too far down the rabbit hole; Nintendo's placed a hard cap of 3,000 Poké Diamonds on your total purchasing power, which comes to around $30/€30/£27, depending on what quantities you buy them in. It's a nice touch that's indicative of a much more muted microtransaction system than the one found in Pokémon Shuffle; the only mildly scummy feature is that you'll be prompted for 2 Poké Diamonds to continue where you left off if you end up failing a mission, which - considering you'll still keep any Pokémon you captured regardless - is simply never worth it.

Even after you've exhausted all your Balloons and overcome the available Challenges, there's still more to do in Rumble World, especially if you're into customization. Aside from Hot Air Balloons and upgrades, the castle store sells everything you need to kit out your Mii in style, including clothes, costumes, backgrounds, and frames that can be purchased with Poké Coins (the abundant in-game currency that drops from defeated Pokémon), Poké Diamonds, or unlocked by ranking up from capturing lots of Pokémon. With these items in tow, you can create a personalized diorama with your Mii and up to three companion Pokémon, and share it with the world via StreetPass.

Profile swapping, while surprisingly addictive, is just the start of Pokémon Rumble World's extensive connectivity features. You can populate your castle plaza with Miis you meet not only from StreetPass, but also from your 3DS Friend List (via SpotPass), and by calling random players in over the internet once per day, ala Bravely Default. This is a great feature in and of itself - we'd love to see more games with asynchronous play tap into the Friend List in addition to StreetPass - but what's really impressive is how well the visiting Miis are integrated into the gameplay.

Once a Mii appears in your plaza, you can talk to them to see their profile card and diorama, learn about their companion Pokémon, and even hitch a ride to their favourite area - a great chance to pick up some rare monsters - in exchange for Poké Coins or Poké Diamonds. You'll pick up bonus Diamonds for reaching certain hospitality milestones, and you might also find your friends working in your castle store, recommending outfits and backgrounds, or playing different parts in the cutscenes that introduce the King's Challenges. Best of all, you'll routinely run into Miis while roaming the dungeons, and if you can save them from wild Pokémon pursuers, they'll follow you around for the rest of the stage, slinging helpful support items like X Attack or Potions.

Seeing your friends running the shop, walking around the plaza, and exploring the dungeons adds a wonderfully personal touch to Rumble World that makes it fun to check in just to see what everyone's up to. In fact, with a steady stream of Miis coming in from StreetPass, SpotPass, and the wider world, it feels a bit like a lost StreetPass Plaza game, and the Mii integration goes a long way towards keeping things fresh and fun as you play.

In terms of presentation, Rumble World goes for adorable art direction over technically impressive graphics, and it does a good job making everything feel accessible and fun. The chunky character models and low-poly Pokémon are endearing, and work well within the toybox theme, though the backgrounds are a bit hit or miss; there are some truly beautiful stages - like a treetop level with paths winding through a multilayered canopy - but far too many are forgettable. The same inconsistency applies to the stereoscopic 3D effect, too: it's put to great use in profile dioramas and when captured Pokémon go flying in towards the screen, but it's entirely absent from the pre-Challenge cutscenes. Overall, however, the aesthetic wins out - Rumble World isn't a gorgeous game, but it's certainly appealing. The music follows suit, with upbeat, bouncy tracks, and while there's nothing particularly 'Pokémony' about it - no main series remixes here - it's catchy and fun.

Conclusion

Pokémon Rumble World takes the basic beatdown gameplay the spin-off series is known for and combines it with fun connectivity features that give it a uniquely social feel. It's not a particularly deep experience, but the blend of button mashing and creature collecting makes for satisfyingly straightforward fun. The toy Pokémon are adorable, the simple combat is accessible and enjoyable, and the level progression system is perfect for playing in short bursts - add in a genuinely generous free-play model, and there's no reason not to give it a go.