Z-Rox is another member of a rare category of games: games that I started before they got badges. Actually, I played through Z-Rox not even really expecting it to necessarily get badges, so I was pleasantly surprised when it did get badges (and a little surprised that they had even added a badge for a part of the game that I hadn't tried and wouldn't have ordinarily expected to get a badge). Why did I play it? Because it was a fun little game and a perfect Flash puzzle game: a very simple concept implemented well.
As the creator's note comments, Z-Rox is really a 1-D game. It's a little tricky for me to explain how the game works -- it's probably simplest to just play -- but I'll give it a try. Imagine a letter, and imagine a horizontal line scanning down across the letter. What is displayed on the screen is the intersection of the horizontal line with the letter over time. For instance, for a T, you would see a long line at the beginning (the crossbar), and then you'd see a shorter line which lasted for a longer amount of time (the stem). (If you want to think of it in a slightly geekier way, you could say that the y-axis has been changed into a time axis.) It's an incredibly intuitive concept. The object displays on a continuous loop, so if you don't get it the first time (and, when it gets to the harder ones, you probably won't), you can keep looking at it until it finally clicks.
The game features a total of 100 levels, starting out with easy letters and numbers, moving into punctuation and simple geometric shapes, and then featuring in the later levels quite a dizzying assortment of objects and symbols. You make your guesses by typing in the answer at the bottom of the screen, which is pretty simple for the letters but can occasionally get tricky for the more complicated objects. The game generally does do a good job of providing a wide spectrum of alternate answers, but there were a couple where we figured out what it was but couldn't quite figure out what the game wanted us to call it. That was a little frustrating, but it was by no means the norm. There are also a couple of alternate modes unlocked as you play through the game: Limited View mode only displays an object once; you can redisplay it, but you only have a limited number of redisplays available. In Random Attack mode, you have a limited amount of time to solve some random objects; successfully identifying an object restores some time to the clock.
The graphics are pretty simple -- beyond the objects themselves, there's not very much. The sound effects aren't particularly fancy, but they're well-chosen and add a nice feeling to the game. The music is really quite excellent -- it's beautiful and relaxing without being obtrusive, and is very pleasant to listen to, even when you're completely stumped by one of the puzzles.
Overall, Z-Rox is an excellent little puzzle. It does get pretty tricky in the later levels, so I recommend playing with other people; having a whiteboard or equivalent to draw on can also be very useful. But it's fundamentally an interesting concept, and the implementation is good. 100 levels is maybe a little too many; a few of the later objects are kind of peculiar, but there's nothing totally unfair, and you can always come back to a level later if you're having difficulty -- this is really a good game to play a bit at a time. All in all, it's a fun diversion.