Nintendo's relationship with mobile games and apps has been slightly awkward to date, as a prolonged period of resistance to the sector eventually turned into a necessary embrace. In its previous efforts on mobile - Miitomo and Super Mario Run - Nintendo has either retained noble intentions (as per the former) or tried to stick to the old model of "here's a good game, pay for it up front". Fire Emblem Heroes, ultimately, represents a tipping point where Nintendo has embraced the good, bad and - almost - the money-grubbing of mobile games. It's not gone entirely off the cliff into the worst practices of smart device games, but any pretence that Nintendo is 'above' those tendencies has whittled away.

Of all of the announced projects to date, Fire Emblem Heroes always had the most potential to be a typical free-to-start mobile game - strategy and battle-centric games are among the most popular to be found on iOS and Android, after all. The bonus, of course, is that the series - particularly with its successful 3DS releases - has earned a lot of goodwill, with Intelligent Systems producing smart, compulsive games. In that respect, adapting the formula for mobile has been relatively straightforward.

What we have here is the essence of Fire Emblem distilled aggressively down to its core parts. The more complex aspects of the main series games such as inventory management, relationship building, unit team-ups and more, are missing. What we have is the familiar Weapon Triangle and self-contained battles on smaller maps, with characters also being limited in how far they can move. Some of the battlefields still have nice twists, such as destructible walls and mountains that force each side into intense head-to-head confrontations, but it's more a battle of power than intelligence. It's fun and quite compulsive, ideal for short play sessions in particular, but any that play for longer periods may desire more complexity and tactical challenge. You could never get far in the 3DS games without levelling up your units, of course, but here the brute force of your fighters is more important than ever.

The app starts off rather generously, to the point that early on you get a lot of bang for no bucks. You get starter characters in each core category (one for each colour element in the Weapon Triangle and a ranged attacker) and it throws bonuses at you with merry abandon. Multi-coloured shards and crystals enable you to fast-track level-ups, and through the app and My Nintendo you can also rack up quite a lot of orbs - the key in-game currency. Indeed, spending a fair chunk of these orbs on ranking up your castle is vital, as that enables units to earn more experience points for their actions.

The story is the first port of call, with the early parts serving as a tutorial and means of unlocking new content. Perhaps to be expected considering the extraordinary and distracting 'main series' workload for Intelligent Systems and the fact this is a free mobile game, the plot's rather thin. The idea is that different 'worlds' - representing Fire Emblem games from across its series history - are being invaded, and Heroes are being contracted to defend their lands from your band of noble liberators. It's a tad messy, and it's all rather throwaway and unimportant, with brief text-based cutscenes playing out at the start and end of each chapter - these chapters have five levels each. It falls a long way short of the storytelling in the main games, but even disregarding that legacy it's fluff by any standards, just there to fill a little space as you rattle through battles.

That's not necessarily a major problem, but it does feel like a missed opportunity. For example, each chapter may be based on a world and set of characters from the IP's history, but there's little context given through the storytelling. Anyone that's not studied Wikis on the series will likely have little idea who these characters are or what worlds they represent. It doesn't harm Fire Emblem Heroes a great deal, but considering the effort undertaken to add so many characters and give them all short profiles - which enthusiasts can seek out - it seems odd that the storytelling doesn't do more to pass that rich history on to the player. The information is there for fans to find, but will inevitably pass by a lot of more casual players.

Other modes are also available with progress, and these are key for grinding (along with 'hard' and 'lunatic' versions of Story missions). Special Maps change frequently and enable you to pick up new characters and useful items, 'Arena Duels' puts you up against the uploaded teams of other players (with AI controlling them), and the Training Tower puts you to the test in exchange for useful items such as those shards and crystals. Working through these regularly is important - the basic gameplay is the same across all modes, but their rewards and experience points become vital.

Driving all of this is a substantial in-game economy and inventory setup, which keeps you well stocked early on. Items for accelerated levelling up, topping up Stamina - which is needed to play - and even reviving your team after failure are plentiful initially. Promotional messages give you little top-ups, and there's solid momentum in the first 2-3 hours; you can spend nothing and, in that time, get quite a bit of enjoyable gameplay. As mentioned above, it's simplistic tactical combat, but it's well-suited to idly passing a little time - it helps that on our device (a Sony Experia Z5 Compact) the app loads quickly and battles can be rattled through in a few minutes.

After that honeymoon, though, the grinding begins, and the game starts to aggressively seek your money in exchange for orbs. The final third of the story demands more powerful units, and the requirements for taking them beyond level 20 are borderline ludicrous at this stage. It's here you realise that your starter units - which are low in rarity 'star' ratings - may not quite cut it, and you're tempted to 'Summon'. It's here where most orbs are spent in a 'Gacha' game of chance, as you sink currency into betting for better characters. This is a luck-based revenue model that's hugely successful in Japan, but understandably has its share of critics.

It does feel like a true game of chance, too. It's five orbs for an initial bet, and the more summons you try in a row the cheaper it gets, to the point you can bet up to five times in one go for 20 orbs. In one two-bet try we got a four-star Marth, but in a separate attempt where we bet the full number of orbs on five characters we had disappointing results. The desire for a five-star hero could drive some, undoubtedly, to gamble - then, beyond that, you'll have to grind up their levels as they start at level 1. Grinding battles uses stamina, and when that's empty you need to refill it with, yep, an orb. The game has given early-adopters a lot of 'stamina potions' to help with this, so that's a problem for quite a bit further down the road.

Ultimately, this Gacha element is entirely optional; after all, it's only necessary if you want to create amazing and varied teams and beat all-comers (and the later parts of the Story). What you get for free, should you ignore all this, is pretty darn good, as it's slick and enjoyable mobile gaming that, for a few hours, keeps you interested without asking for more. For those seeking a free bit of entertainment, it's an excellent offering.

It could have been better, though, and there's scope for Heroes to improve in the future. It lacks some of the hooks that suit other mobile titles in this genre, such as real-time online battles or clans. A surprising missed opportunity is the Castle, which is really a fancy hub for accessing rewards, messages or adding friends with codes (those confounded things, again); it can only be tweaked with a handful of basic aesthetic choices. The 'My Castle' element seen in Fire Emblem Fates would have actually suited mobile down to the ground, and added a bit of extra variety beyond team building and quickfire battles. That Fates-style home base mechanic would also work well for online invasions and defences, rather than the random battle maps we get at present.

The lingering feeling of missed chances, however, doesn't extend to the presentation, which deserves praise. Graphically it's an attractive game, opting for slightly cleaner and more modern character designs (in battles) than the 3DS titles, with some fun animation flourishes for special moves. It's all rather slick, and little touches like a decent range of voiced lines and some high quality music give this game a premium sheen. Nintendo, undoubtedly, is finding its feet in terms of delivering attractive mobile games.

Beyond that, some will wonder about battery and data usage. This game is a bit of a battery hog, which can only be minimised to a minor degree by turning off sound and limiting the length of battles by taking out some animations. It's not as bad as launch period Miitomo was in its full graphics setting, but short and snappy sessions are advisable on the go. Like many mobile games, meanwhile, the game wants a connection to play. A positive is that it seems happy with a typical 3G connection, and when we unhooked from Wi-Fi to test it a 20 minute play session only used a small amount of data. It seems well optimised assuming, once again, players don't settle in and play for an extended period without Wi-Fi and a power point nearby.

Conclusion

All told, Fire Emblem Heroes is a slick, well-presented and fun 'lite' take on the series. It's heavily stripped down from the core games, and is best enjoyed in short bursts, but serves that purpose well while wrapping the experience in a stylish UI with handsome graphics and a typically lustrous soundtrack. Nevertheless it's a limited game, and after a generous opening of playing for free the 'pay-to-win' element starts to take over. It's here that many will likely shrug and move on, having had a decent fill for no investment - for completionists, however, there's plenty of grinding (and likely some expenditure) awaiting them on the journey.