I'm already pretty cynical about Nintendo's seemingly lacklustre attitude to the download-only DSiWare service. It launched with some interesting games, such as Art Style: CODE (as well as some terrible ones, like Art Style: AQUITE) but there hasn't been much direction in terms of what's been released since.

Equally, the idea of these A Little Bit of... titles - the majority of which are repackaged slices of games previously released on a standard DS cartridge - appears to be something of a cheap trick, especially in the case of games such as Brain Training and Magic Made Fun.

Happily, though, A Little Bit of... Dr Mario (which was released in North America as Dr Mario Express), is a great puzzle game.

Sure, in typical Nintendo style it's been released in numerous different versions since 1990s, but as a twist on the colour-matching genre it's a classic, and this DSi version is both fun and challenging.

The core of the game sees you presented with an 8x16 block grid, onto which yellow, blue and red viruses are positioned. The harder the level, the more viruses are pre-positioned.

The game starts as Dr Mario hands you coloured capsules. These are either two-toned (yellow-red, red-blue or blue-yellow), or completely yellow, red or blue. As each is placed onto the grid, you can rotate them using the A and B buttons and move them as they fall with the D-pad.

Other control options include a fast fall, which you execute by pressing down on the D-pad. Capsules can also be rotated into place while they’re falling - i.e., rotated on the spot - enabling you to get them slotted into concave points. This is one of the game’s key manoeuvres.

Your goal is to match four or more of the same colour - whether virus or capsule. Doing this makes them disappear, so you have to clear all the viruses from the grid in the fastest possible time. If, however, a capsule stack touches the top of the screen, it's Game Over.

So far, so simple. Only Dr Mario is anything but a simple game. This is mainly due to the pre-positioning of the viruses around the grid.

High ones can usually be quickly dispatched, but ones lower down the screen become increasingly blocked off as the game progresses and more capsules fall. This means you're always trying to balance the immediate desire of clearing easily accessible viruses with trying to carefully stack and remove capsules that are useless for that immediate task.

What makes it harder is that misaligning a couple of capsules early in the game can result in minutes of careful repair work. And at any time the game can quickly turn against the player, meaning full concentration is required.

Still, if the test offered by Dr Mario remains as taut and enjoyable as ever, the presentation of A Little Bit of... Dr Mario is anything but. It feels like someone has taken an old SNES or Game Boy version and slapped it into place in the DSi Shop with a mallet.

The biggest issue is the size of the grid. It's tiny and tucked away on the left hand side of the bottom screen (the game doesn't actually use the touchscreen, it's all key-based). Obviously, the DS's dual screens aren't conductive to this sort of column-based game, but with Tetris DS Nintendo managed to get around the problem with great design.

In the case of A Little Bit of... Dr Mario, the graphics - in particular the virus sprites - are terribly old fashioned and badly animated, which makes them difficult to concentrate on.

This is situation is further confused by the ghosting option, which enables you to see where capsules will slot into place on the grid. It's so badly implemented I had to switch it off. Moreover, the grid has a brown background, which clashes with the red colour.

Continuing in this vein, when you start the Classic mode, you're thrown into level 10 of the 20 available. Actually, it's even more confusing because the levels are based on their difficulty, but for some reason you don't automatically start at the easiest 00 level.

As well as the solo Classic mode, you can play against the computer in the VS CPU mode. Neatly, this allows you to set separate difficulty levels for yourself and the CPU. The mode works by sending over additional coloured blocks to your opponent as you clear the viruses from your grid. There’s no multiplayer mode, though.

Sadly, then, A Little Bit of... Dr Mario provides another example of Nintendo's current lack of attention for the DSiWare concept.

At least compared to games such as Paper Plane and Art Style: AQUITE, Dr Mario is a really good experience: to that extent it's well worth the 500 Nintendo Points (£4.50, $5, €5) it costs. But with a little more love and polish, this could have been a superb addition to the DSi software library. Instead, it feels more like a scraping from the barrel.