King.com's phenomenally successful puzzle-shooter Bubble Witch Saga made the leap from Facebook to iOS at the end of July.

While that may seem like a redundant statement, without it you might look at the Bubble Witch Saga icon on the App Store and think, "What's the big deal?"

The big deal is that Bubble Witch Saga boasts 4.8 million daily players on Facebook. More saliently, King.com also reckons it's the first game to sync between Facebook and iOS, so you can end a session on iPad and resume it on PC.

Every little thing she does

Light in plot (there are three witches standing around a cauldron that belches multi-coloured bubbles out every so often), and only fair in music, Bubble Witch Saga thankfully compensates with above average graphics and a solid, intuitive gameplay style that never ceases to provide a challenge.

The basic gameplay is like Bust-a-Move mixed with Peggle and a dash of Arkanoid. You shoot a bubble of a given colour up into the game field and match it with two or more bubbles of the same colour. When you match the bubbles up they disappear.

To clear a level you have to free up nine of the uppermost slots, sending all remaining bubbles down to the floor. On their way down, they bounce Peggle-style off an array of hovering spiders before landing in smaller cauldrons labelled with different point awards.

The more spiders you've generated - by clearing the screen using as few bubbles as possible - the more likely they are to multiply your score.

Of course, this approach introduces an unwelcome level of randomisation to the scoring process: even levels you think you've aced can end up yielding one star or fewer if the bubbles happen to bounce unfavourably.

And you need to have gained at least one star to successfully move onto the next level.

Suffer a witch to live

To help you, the freemium nature of Bubble Witch Saga necessitates in-app purchases, and King.com is not shy about the prices.

You can elect to buy charms (for $7.99/£5.99) that bestow permanent power-ups on you or increase your number of lives. Given that Bubble Witch Saga contains 150 levels, this price may not be too high for those interested in exploring all that it has to offer.

When you run out of lives, the game makes you wait 30 minutes until you can play again. To circumvent this limitation, you can ask your Facebook friends for help or buy another go for 69p.

While expensive at £5.99, the Charm of Life IAP is almost worth it to keep Facebook spam and the mounting cost of micro-transactions at arms' length. Or you can just wait, of course.

Overall, it's difficult to not enjoy Bubble Witch Saga. The gameplay is simple, certainly, but its balance of skill and luck is well-judged and there's plenty of compulsive fun to be had.