Sure, a version of the game is available for free, but the addition of multiplayer and a new level set more than make it worthwhile. The graphics certainly aren’t the height of beauty, but when did the quality of a game start being measured in such terms? No one thinks less of the gameplay in Super Mario Bros. knowing that the bushes are re-coloured clouds. The graphics in N+ are sharp and functional; which, in a game such as this, is much preferable to pretty colours and needless distractions. And the size of the game? Well, Sonic the Hedgehog weighs in at well below 13MB and is as excellent today as it was in 1991.

The first thing to do when starting N+ is to forget everything you’ve learned in years of mastering those Mario and Sonic games. While it’s most definitely a platform game at heart, the gravity in N+ works very differently to other examples in the genre. Your ninja is far more floaty (as if set on the moon), which gives increased control over jumps. A leap can be fine-tuned until the very point of landing, to avoid rogue mines or reach tiny platforms. The physics do take some getting used to, but once they click you won't want them any other way. Performing inch-perfect jumps and taking advantage of terrain to leap huge distances soon becomes second nature.

The aim of N+’s hundreds of levels is simply to unlock and reach the exit before the time runs out or one of the enemies gets to your ninja. Each episode contains five levels, and the time is carried over from one level to the next until the episode is complete. Rushing through levels is the simplest way to get to the next, but, by the fourth and fifth level, time will often be running low. Collecting pieces of gold around each level (every piece adding a few seconds) is, therefore, essential, and more so with the leader-boards being based on the time remaining at the end of each episode.

Collecting gold soon becomes very addictive and adds an entirely new and different way of playing the game. It’s possible to complete the game with a minimum of gold, but planning and executing routes through each level to collect the maximum amount of gold is immensely satisfying. As if it needed any help in this matter, this makes the game even harder.

You will die; a lot. Missiles will unflinchingly trail you around the entire level and will invariably hit their target, unless outsmarted. Machine guns launch a barrage of bullets in the general direction of the ninja. Lasers laser, snipers snipe. Add to that a number of drones that follow set patterns, or are proximity-triggered, for a game that revels in death; a lot of death; hilarious, hilarious death. Dying creates explosions of blood, and sends limbs flying everywhere – triggering mines and nearby enemies – and is amusing enough to make dying much easier to take. The best thing about all that death, though, is that practice really does make perfect. By observing each enemy, tricks can be developed to play with and mock them; eventually nothing will stand in your way.

Never is this more apparent than with the game's now infamous difficulty spikes. Simply skipping an episode that seems impossible and returning later, will see you armed with skills you didn’t even know you had as you teach the game who’s boss. If you still can’t manage, then help can be enlisted with one of the game's multiplayer modes. Race and Survival are fairly self-explanatory, and very simple games. The real fun, however, comes in co-op mode.

If desperately stuck, the single player episodes can all be played in co-op with 2-4 players, but a number of specific co-op maps are also provided which are downright clever in their design. Players are usually started at different start points and their own actions directly affect the other players. Sometimes, switches must be hit on one path to allow players on the second path to progress, and then the favour returned until everyone reaches their goal (be it the switch or the door).Other times, one player is simply tasked with surviving, while the other player slowly makes his way toward a switch at the end of a prescribed route. Still other levels employ other little tricks and it’s great working them out and working together to beat them. Offline, the co-op is even better, with the ability to swap controllers over to try the other person’s path and show them how it’s done – or not done. Future map-packs promise more of these levels and will – no doubt – be an essential purchase.

The level editor provides a similar joy to the paint job editor present in Forza 2. A series of basic shapes (as well as the various enemies and other artefacts) are provided with which single-player or multi-player levels can be made. At first it seems restrictive, but soon you realise you can create almost any design, with a series of videos of user-made levels online proving that the only restriction is your imagination – as the old cliché goes. Unfortunately, video-sharing websites are the primary source for user-created levels, as Microsoft has denied Metanet the ability to implement a full level-sharing feature. They can be played online with friends, however.

There’s a simple way to establish whether someone's played N+; simply listen to them talk about it. “It’s the best 800 points I’ve ever spent,” they’ll wisely convey. There’s simply so much game here, and so much replay value to be found in pursuing high scores that - for not much more than a fiver - it’d be rude not to buy it.