N is the best Flash game I have ever played, so discard any expectations of objectivity. If you are no longer interested in reading the review, I advise you to form your own opinion by downloading it here.
Everybody else, feel free to continue reading.
As mentioned above, N is written in Flash, and is thus available for Windows, Mac, and Linux, in no particular order. Unlike virtually every other Flash game I've played, the purpose of N is not to display advertisements, or nag you to register; it is an actual videogame. The genre is an old favorite of mine, the 2d platformer, and the difficulty is reminiscent of Contra without the infamous Konami code. This, in spite of the fact that you have infinite lives.
Yes, that's right. Infinite lives. You may continue playing until you give up in frustration. But I get ahead of myself. N puts you in a level, all of which is visible with no scrolling, in the style of Donkey Kong. You are a very well animated Ninja, and your goal is to exit the level within the time limit. There are gold coins, too, and each adds two seconds to your time. So far, par for the course. What sets N apart from the myriad similar games is a physics engine that makes it almost as much fun to kill the ninja as it is to strive for the exit. To my knowledge, it is the first use of ragdoll physics in a 2d game, although if I'm wrong, I'm sure I'll be corrected.
The first few levels are a slow warm up, allowing you to grow comfortable with wall jumping and the additional demands the physics engine adds to controlling the Ninja. On level three, mines show up, and not two long after that... robots, the sworn enemy of all ninjas. The enemy AI is among the best I've seen in such a simple game, and even after you learn its rules, it is still challenging. Not too long after that, the game becomes so demanding you'll find yourself biting back curses like Yosemite Sam with each of your deaths. And those deaths, I'm sorry to say, are your fault. The simple controls (left and right arrows to walk; spacebar to jump) leave no room to blame anyone else, which is a hallmark of many great games.
With over 200 levels, a price of free, and able to fit on a floppy disk, I would say that most Flash-capable computers should be able to find room for N on their hard drive. Note: Go into options and set spacebar as the Jump key. You're only setting yourself up for heartbreak otherwise.