If you're confused by the appearance of Angry Birds 2, the sequel to Rovio Entertainment's hit game, it's understandable. It's not the second game in the series; there are more than 10 versions featuring the Angry Birds, including Angry Birds Seasons, Transformers, Star Wars and Angry Birds Go, the racing version of the game.

Billing itself as bigger, badder and birdier, Angry Birds 2 is really aiming high. Unfortunately, it falls short of the mark, mainly due to some questionable decisions that mess around with what I really loved about Angry Birds to start with.

Even if you can get over the heavy The latest version is, unlike the original, free to play. But as you might expect, it brings in the in-app purchases in force to make up for it.

Part of the original’s appeal was in figuring out the puzzles. You were given your stock of birds for each level, and you had to figure out how to best deploy them for maximum impact. When they were used, you were done and if you hadn’t managed to take out the egg-thieving pigs entirely, you had to start the level all over again.

A few tweaks would usually get you over the one-star hump, but three-starring all the levels was the ultimate goal.

Angry Birds 2 messes with that formula a little too much. It started off well by adding more than one "room" to all the levels, but any additional challenge and subsequent sense of achievement that may have brought is quickly drowned out.

The levels are now randomised. Yes, randomised. So you aren’t always going to play the same level over and over again, even if you fail to complete it. That’s fine if you want variety and have a low boredom threshold, but the beauty in the original was that you could plot your strategy over a couple of attempts before pulling off the three star performance of your life.

Which brings me to another problem. You also have limited lives before you have to either pay to refill them, or wait it out til they replenish. That kills off the compulsive aspect of Angry Birds right there.

The compromise is that you can pay with gems you earn in the game, but the cost per refill is so high that you’d eventually have to dip into your real-world cash reserves to keep playing. Those gems can also be used to retry the level you are playing if you fail to destroy all the pigs.

But maybe I’m being a tad negative here. There have been a few tweaks that work in its favour. You are rewarded for destroying as much of the scenery as possible through a gold bar in the top corner of the screen; fill that bar and you’re awarded an extra card, usually bird but occasionally a spell (we’ll deal with those later). That can mean the difference between retrying the level or completing it.

There are also some helpers you can call on, in the form of spells. These range from a card that turns the structures to ice, making them easier to smash, to gold ducks raining from the sky.

You can also use debris against the pigs, with fans that can be a hindrance at times but at others help you direct a wayward piece of rock into the pigs. Plants will also randomly gobble up debris and fire it back out, which can take out a few straggler enemies.

There are boss levels too, which will pit you against an enemy that’s a bit tougher to deal with.

And there are some new animations. Pull back on the catapult and you’ll see a close up of the bird’s face, with a suitably menacing expression, before its switches to the freaked out pig targets. An explosion can send a pig and bits of scenery careening into your screen. It’s a nice touch.

But ultimately, it's not enough to make Angry Birds 2 anywhere near as compelling as it first iteration. In saying that, it's riding high in the Apple charts, and it's had more than 10 million downloads since its launch on mobile and tablet. Despite its apparent popularity, it's currently in high 80s on the list of top-grossing games. To put that in context, Candy Crush is number three with Minecraft at number 15.

The original Angry Birds was a fixture in the charts for a long time after the initial flurry of popularity. The real test for Angry Birds 2 will be how many people are still playing it in a few weeks time. I don't think I'll be among them.