If you believe the newspaper headlines, the current generation of school leavers can boast remarkable exam results. Sadly, they can't spell the names of the subjects they took or add up how many passes they got.

Let's be thankful for small mercies, as iPhone developers seem to be taking the lead started by Nintendo's Brain Training and releasing games that encourage us to improve our basic maths skills.

For example, there's DropSum and Big Top 10, which have you adding up chains of numbers to make totals of 9 and 10 respectively.

Addicus is more freeform in nature, as you have to add up numbers to meet the changing totals provided in the top-left corner of the screen.

And, like the Brain Training's Stroop Test, it mixes in colours, so if you can see a blue '10', you can only tap on blue-numbered mushrooms to make your sum. It's the same for yellow and red. If the required number is white, however, you can use mushrooms of any colour to make up the total.

It's a neat, if simple, trick because the colour variation gets you thinking that little bit more, and with the clock counting down for each number sum you don't have a lot of time to ponder anyhow. Indeed, despite its seemingly easygoing manner, as you scroll from a completed mushroom screen to hopefully to-be-completed mushroom screen Addicus starts to build up pace.

If you're doing really well, you end up in Overdrive mode where you rack up more points - something you can also accomplish by using double numbers and flushes to complete your sums. There are other secret combos for you to discover, too.

To be honest, though, you probably won't be playing Addicus for vast periods of time, but because the games are quick - you could even argue a little hard - you will end up playing multiple times. In that respect, it's a little like App Store classic Doodle Jump in terms of its just-one-more-go quality.

Wider competition is encouraged with OpenFeint integration so you can see where you rank in terms of global high scores, and there's Facebook and Twitter notification as well.

Rounding out the release - a debut for Canadian start up Get Set Games - is the game's bouncy presentation, with colourful graphics and upbeat music combining to make Addicus a nice little package. It won't revolutionise the genre, of course, but it will provide you with plenty of number-crunching highs and lows.