Pokémon have been puzzling ever since the Johto days, when Pokémon Puzzle Challenge married the block-flipping gameplay of Panel de Pon with Game Freak's charming, collectable characters. It's a formula that's stuck, with Denpa Men developer Genius Sonority heading up the most recent series of Poké-puzzle combinations, including Pokémon Shuffle, a game that has the dubious honour - Rusty's Real Deal Baseball antics aside - of being Nintendo's first foray into the mobile-style model of free-to-play pricing. The microtransactions are unquestionably off-putting, but provided you're able to ignore them, Pokémon Shuffle is definitely worth a download - it's an excellent match-three game with fun mechanics and plenty of Poké-charm.

Like its predecessor, Pokémon Battle Trozei / Pokémon Link: Battle!, Pokémon Shuffle uses a match-three mechanic as its main gameplay hook. Presented with a 6x6 grid of smiling, spherical Pokémon on the touchscreen, players use the stylus to swap pieces and attempt to match three-or-more-of-a-kind, dealing damage to the wild Pokémon on the 3DS' top screen in the process. Unlike Battle Trozei, however, Shuffle is a move-based puzzler; in each of the 150+ stages, you'll have only a certain number of swaps to defeat your opponent, and if you can't wear them down in time they'll run back into the safety of the tall grass.

If you do manage to win the battle within the allotted number of moves, you'll have the chance to catch the opposing Pokémon and add them to your team. The catch rate is pre-set in percentages for each 'mon - from the high-nineties for Route 1 standbys to laughably low numbers for more prestigious Pokémon - and though holding 'Down' and 'B' won't help your chances, efficient puzzling will: for each move remaining once you've defeated a Pokémon, you'll get a catchability boost on the percentage bar. It's still no guarantee, but it's a satisfying reward for skilful play; we raised a Dragonair's catch rate from 2% to 57% by finishing the fifteen-move stage in seven turns.

You'll want to round up as many monsters as you can, because you can choose up to four to bring into each battle, and - true to its roots - Shuffle places a huge emphasis on each Pokémon's individual abilities. They'll gain experience points and level up as you go, and the series' 18-way chain of strengths and weaknesses is in effect here, so that Pokémon who are strong against the stage's Type will do double damage. Each monster also has a special power, that can do everything from increasing damage in a four- or five-way match to inflicting status ailments on the enemy, like Freeze, Burn or Paralysis.

These last powers are particularly helpful, because when they're not encased in ice or nursing a burn, wild Pokémon will fight back. Each one has a different offensive strategy, from creating junk blocks to 'freezing' tiles in place, and a countdown timer on the top screen shows you how many turns you have before the next attack. Matching adjacent tiles can clear some of these obstructions, but a more effective technique lies in Pokémon Shuffle's take of the franchise's newest trick: Mega Evolution.

Provided you have the appropriate stone - earned in Trainer Battles every 15 stages - certain Pokémon you'll pick up along your journey can Mega Evolve. Once you match enough of them up in a stage they'll morph into their final form and evoke a range of associated screen-clearing powers. From there on out, matching Mega-Evolved Pokémon will clear out tiles in a pattern unique to each 'mon - Mega Mawlie cuts diagonal swaths through the board, for instance, while Mega Sableye clears out a wide ring around the edges. These techniques do plenty of damage, and - by rearranging a significant portion of the board - frequently lead to spectacular combos.

Match-three games are almost a guaranteed good time if done right, and Shuffle certainly gets it right - the move-based puzzling makes for a measured, cerebral experience that rewards planning ahead and a keen eye for combos. But what makes it so much fun to play is how well everything fits together; the Pokémon powers and Mega Evolution interact to encourage surprisingly deep strategic play, especially in choosing your team.

Togetic may have a low attack, for example, but its Pixie Power ability - which increases the damage done by any Fairy types in a combo - makes it a perfect pick for a Fairy-packed team pitted against Dragons or Dark opponents. Mega Sableye has a screen-sweeping clear pattern that runs rings around Mega Audino's one-tile-adjacent range, but it also requires more matches to Mega-Evolve; in a stage that's short on turns, bringing in Audino instead could be tip the scales towards a combo-heavy win. These types of decisions mean that much more than just luck goes into each round, and help keep the action exciting as you unlock more monsters and powers along the way.

Along with the standard stages, Pokémon Shuffle throws in ten Expert levels that unlock gradually as you progress. These play more like Battle Trozei, in that you'll have an unlimited number of moves but a set amount of time, and need to work fast to make as many matches as you can before the timer runs out. Living up to their name, these levels are tough, but they also feature some of the most sought-after Pokémon - like Venosaur, Blastoise and Charizard - and make for a nice change of pace from the main game.

There are also time-sensitive Special stages, beamed down through SpotPass, that offer their another variation on the catch-'em-all theme. At the time of writing, these include an encounter with a catchable Mew - much to the delight of every childhood Red and Blue player - a 'Pokémon of the Day' stage featuring a rotating selection of Rotoms, and a Meowth market where players can earn some extra cash by matching coin tokens during the round.

With its deliberate pace and strategic play, Pokémon Shuffle feels like a very different game from Battle Trozei - but in terms of visual style, they're very much cut from the same cloth. As in its predecessor there's no 3D effect, but it uses a clean, colourful look that's bright and appealing. Somewhat surprising, however, is the fact that outside of the monster icons on the touchscreen, there's very little that feels distinctively 'Pokémon' in the presentation. That's not necessarily a negative; stage backgrounds are varied and fun - including a night market, a desert bazaar and a marble museum - and the pastel colours are inviting, so even if it's not the fan-service bonanza it easily could have been, it's still relentlessly charming.

The soundtrack similarly shies away from main series remixes, instead giving off a Mr. Driller-style 'world music' vibe with a different catchy song for each in-game region - like koto tunes for the night market and calypso for the beach - while the sound effects, full of cascading chimes that climb with each combo link, remind us more of Disney's TsumTsum than anything in Game Freak's stable.

Finally, it would be impossible to wrap up a review of Pokémon Shuffle without touching on the title's microtransaction-laden pricing structure, and unfortunately - if perhaps predictably - it's the title's biggest misstep. Time-restricted play is the main issue at hand; each time you play a stage, win or loose, you'll use up one of five Hearts. Up to five hearts automatically regenerate, but only after a half-hour each, and since each stage lasts anywhere from thirty seconds to a few minutes, the end result is five to fifteen minutes of play for every two and a half hours of rest. As a time-to-time distraction on your 3DS, we'd say that's pretty much perfect - but if you find yourself wanting to play on, things get a little stickier.

Jewels are the main in-game currency, and you can buy them with real-life cash, either one at a time for $.99/€.99/£.89, or in larger quantities at a slight bulk discount. You can then exchange them in the in-game shop for either Hearts or Coins - the latter used to purchase power-ups and Great Balls, which can increase your catch-rate with wild Pokémon.

The multiple currencies and exchange rates seem designed to confuse, but worse is the fact that the game appears to actively steer you towards poor purchasing decisions. If you fail a stage, for instance, you'll see a prompt offering to exchange one of your Jewels for five more moves. As a Jewel would elsewhere have a going rate of five more plays, this is a patently terrible deal - and if you really need the extra moves to beat the stage, you could always exchange the Jewel for 3,000 coins, buy a '+5 Moves' power-up before the round, and end up with a cool 2,200 coins left over. No matter how you slice it, either option is far better than getting swindled out of your Jewel for a few measly moves, egged on by the interface. Wheeling-and-dealing was half the fun in Rusty's Real Deal Baseball, but we don't think trying to see through Shuffle's scammy pricing scheme should be part of the metagame here.

The biggest problem - or perhaps the greatest blessing - with Pokémon Shuffle's microtransactions, however, is that they're simply not worth buying. Hearts regenerate slowly but surely, so if you're willing to space out your sessions a bit - which is how we'd suggest it's best enjoyed anyway - you can get through the entire game at a decent pace without exchanging any Jewels at all. And between daily Check-In bonuses and the winnings earned from beating each stage, you'll quickly rack up more than enough Coins to use the only decent power-ups ('Exp x1.3' and the occasional '+5 Moves' for trickier stages), and spring for the occasional Great Ball to lock down a favourite 'mon.

In fact, aside from buying a bucketload of Jewels to play continuously while travelling, we can't think of a single good reason to spend any money on Shuffle. We cleared over 100 of the game's 150+ stages without spending a dime, managed several longer sessions thanks to Jewels earned from Trainer Battles and a few lucky StreetPass hits, and amassed a respectable menagerie of Pocket Monsters using only a few Great Balls purchased entirely with in-game winnings. It's certainly more difficult than taking the paid route, and we failed a few stages several times before finally being able to proceed, but thanks to the excellent underlying gameplay it never stopped being fun.

Conclusion

Pokémon Shuffle is a fantastic match-three puzzle game marred by an uncharacteristically sleazy suite of microtransactions, and your ability to enjoy the former will hinge directly on how well you can ignore the latter. As a game you can pick up and play for a few times each day, Shuffle is a blast - the methodical, move-based matching action, fun implementation of Pokémon powers, and appealing presentation all make for a top-notch puzzler. If you need something you can play for hours at a time, however, your best bet is to ignore the in-game shop altogether; take the money you'd spend on an afternoon's worth of Jewels, put it towards Pokémon Battle Trozei instead, and let the endless supply of Poké-puzzles tide you over between Shuffles.