Plants vs Zombies is one of the most popular gaming apps ever released. And for good reason: it's so good that you'll want to eat your own brain.\nPopcap, the title's developer, has been gobbled up by publishing giant EA since the original game's app-format launch on Apple's iOS in 2010, a move that's led to Plants vs Zombies 2: It's About Time adopting the "freemium" model. That's right, the free-to-download title - affectionately known as PVZ2 to many - comes with in-app purchases to assist progress. But does this mechanic affect the simple joys of gameplay?\nAhead of its official release in the UK we've had Plants vs Zombies 2 on the go for a couple of weeks now. Deep into the game, we've got the lowdown on whether the Popcap-EA alliance brings fresh new fun to the franchise.\nPick your brain\nAt its core Plants vs Zombies 2 is a real-time strategy game. If you're new to the series then a mental groan probably just went off in the back of your mind. But, fear not, the tongue-in-cheek comedic approach and genuinely addictive gameplay make for a strategy game that feels almost removed from its very genre.\nAdvised by the saucepan-hat-wearing Crazy Dave - that establishes the rather silly theme from the off, doesn't it? - it's your job to defend your home ground from a hoarde of slow-moving zombies.\n\nYour only form of defence? Plants, but of course. Magical, power-wielding plants. Sunflowers generate sun over a given period of time which can be used to purchase other defensive and attacking plant types.\nJust like the original title, Plants vs Zombies 2 has a single-screen field of play that's made up of five columns arranged into nine squares apiece. Like we say, that may make it sound rather like a boring, strategic, game-by-numbers title - but it doesn't feel like that in play at all. Quite the opposite.\nZombies advance from the right of the screen and if you don't pop off those zombie heads then first they'll eat your plants, second they'll break your final line of lawnmower defence, before finally chomping down on your brains. If that happens then, well, we needn't explain really: "the zombies ate your brains" and it's level failed, game over.\nThose familiar with the original will find immediate familiarity with the game's look and feel. But that's probably because you haven't played the original title for some time. Side by side, the difference in PVZ2 is crystal clear: it's much smoother and the graphics are far more polished.\n\nThe arcade-style onslaught of the original has been ditched and replaced with a Super Mario-style map system that's easy to navigate and avoids that irritation of getting stuck at a certain point. Here you choose which level you play and replay in order to max out its various star-based difficulty levels.\nOh, and PVZ2 is no longer set in your back yard. Crazy Dave ate a taco so tasty that he wanted to eat it again, and so his trusty time machine, Wendy, took him back in time but - in that Crazy Dave way - messed up and ended up in ancient Egypt. Where, apparently, they had lawnmowers. It's bonkers, but it's still brilliant.\nPlants and power-ups\nAlongside the typical troupe of plants from the original game - including defensive Walnuts that take a heap of zombie-munching before they're defeated, peashoots that shoot peas on the attack and scores of other specialist floral types that would be welcome in Little Shop of Horrors - there are additional new plants in PVZ2.\nWe'll leave you to discover what they all do, as that's part of the fun, but with names like Bonk Choy and Coconut Cannon, you get a rough idea. New plants are a necessity to move the sequal forward and it gives the original formula a fresh new feel.\n\nBut some plants of old have hung up their boots; they've gone. As water-featured levels don't require planting on water in PVZ2 any water-borne plants have vanished from the almanac.\nThe immediate absence of some of the classic plants such as Squash, Snow Pea, Jalapeno, Torchwood and Imitater is a bit of an alarm. These plants aren't missing, however, they're just hiding. Hiding behind a pay-to-unlock scheme. And so here's our first gripe: each of them costs \u00a31.99 to unlock. We get that the game is free to download, but two quid? That's a tenner gone straight away just to open up those five, and then there's an additional locked-down Lily plant that you're likely to want in the later levels. You don't have to buy any of them - we haven't (yet, at least) - but their presence behind the paywall gives a slightly different feel to the game.\n\u00a0\nThere's also the addition of power-ups added in to play. Each lasts for a couple of seconds during which time it's possible to pinch off zombies' heads, swipe and throw zombies from the screen or electrocute groups of them. Nice idea, and one which changes the gameplay mechanic, but one that you'll also need to pay out for.\nFortunately you needn't spend real cash by default: in-game coins can be earned by killing zombies and completing levels, but you can top up that in-game bank account with a real bank account should you so wish. So there's another revenue stream - similar to the original game.\nDuring play the occasional green glowing zombie will venture on screen. These special zombies release plant food which can be collected and used to boost plants with individual supped-up powers. It becomes an essential tool survival so you'll want to stockpile the plant food that you can - it's limited to three slots at the start of the game - and use them intelligently. No plant food? No problem - 1,000 in-game coins will bag you another. However the food doesn't carry over from one level to the next.\n\nThroughout individual worlds there are keys that can be collected and used to unlock gates on the map to add new plants to your rosta, open up special side-mission-style levels and, in some cases, add permanent advances such as starting every level with more sun. Again, spend time playing and these keys will appear naturally - often randomly - during levels, or from Yeti zombie's lunchbox. But if you don't have the patience then gates can be forced open\u2026 with an injection of real cash.\nBankroll: Brain-ache or brainwave?\nDoes all this talk of cash ruin the gameplay though? No. Not at first, anyway. You needn't break open your wallet to enjoy the game, with the possible exception of buying into those classic plants. For the sake of a few quid here and there it's worth it, as PVZ2 brings with it as much fun as a console game in our view (and, funnily enough, it's coming to current- and next-gen consoles in the form of Plants vs Zombies: Garden Warfare in the not-too-distant future).\nHowever, as we've come to play the game more and more it becomes clear that to max out three-star levels that you'll need more than just your wit. You'll need to spend some coinage.\n\u00a0\nHere's why: standard levels are more than approachable, while others - such as the late-on final star of some levels - prove to be a challenge. We like the three-star system as we relish a challenge. But as power-ups cost more coins in later levels than in earlier levels to buy you're likely to want a plant like the Snow Pea or will have to use multiple power-ups to succeed.\nWe like it when the pressure's on during play, for sure, as some levels will take multiple attempts to crack. In part that's due to new mechanics - there are sliding mine carts in the wild west levels where you can move your plants up and down the rows, for example. But other levels we couldn't complete without buying into plant food and\/or using a number of power-ups. Then it feels more spend-o-rama than strategy.\nWhen it comes to replaying said failed levels we'd also like a speed-up option to dash through some of the more boring slow-walking stuff that's typical of the beginning of play. Ignoring the money side of things and that's the only in-game criticism we can throw at the gameplay really. Well, that and that there's not one moment when it's explained how to open up world number four - a silhouette that appears to be set in the space-aged future.\n\nHave we parted with any real-world cash? No, we've not needed to. But we've not managed to achieve every star in every world yet either. Which does make us feel, even if just a little, as though those EA bigwigs' fingers are poked deep into this slice of brain-pie. Fans of the original will notice that the Zen Garden has been steamrollered too, so there's no way to earn coins while away from the game - it's play to earn, or pay to earn. But play we did. It's that obsessive Angry-Birds-like play that'll pull you in - which goes to show how successfully PVZ2 is designed.\nGames need to be profitable and we totally get that. But we'd rather pay out to buy Plants vs Zombies 2 outright rather than dipping in here and there throughout play, or reaching a wall where we had to play a bunch of boring levels just to collect necessary coins. And if we did feel the need to dip in then 69p per add-on would be far more welcome than the \u00a31.99 that's enforced. In the order of things EA has been gentle with the model: this isn't the insane wait-for-five-days-or-pay-now model.