In Cover Orange you do what it says on the tin: cover oranges. Each level begins with one or more oranges sat out in the open, waiting for you to use a set of objects to stop an incoming hail of acidic rain from sending the vitamin C engorged pals to an early grave. While this is an incredibly simple concept, the physics system and genius puzzles make this an iOS game you'll find hard to put down.

In one level you might simply have to knock the oranges into a hole and then cover them with a crate, but another might require the use of numerous objects (barrels, crates, wheels and triangular blocks), moving items such as seesaws and karts, and a complex series of bombs that fire objects around the level. It's fair to say that there's a large amount of trial and error required to complete the more devilish stages, but that's part of Cover Orange's charm.

There are times when it seems luck isn't on your side, with acidic rain drops somehow managing to squeeze through gaps, only for the oranges to remain safe when you try the exact same set-up moments later, but the ideas put into every level mean you're unlikely to get annoyed. Just hit the retry button and you'll be covering those oranges again in no time at all. If you get stuck you can skip on to the next stage, hopeful that when you return you'll have had an epiphany.

I've seen plenty of physics-based puzzle games on the iPhone, but this one has something about it that makes you want to keep playing. Seeing the little oranges quiver and pray for survival as the rain cloud comes over will melt the hearts of anyone with even a small dose of empathy, while seeing them turn to black ash is a sad, hard to watch sequence that you'll vow never cause again.

Cover Orange has already doubled in size since its original release thanks to a considerable amount of free additional content, so it's hard to know how much more will be added in the future, but with 120 levels to complete you're unlikely to finish them all for quite some time. Once you've saved the oranges there's the option to go for high scores, finishing levels as quickly as possible, but I don't think the gameplay suits this type of high score chasing.

This simple but addictive little game might not have the star power of Angry Birds or the score-based draw of Tiny Wings, but it's a brilliant physics-based puzzler that can be enjoyed alone or with friends.