Zilch is a fun little dice game. Like any dice game, there is naturally a large element of luck, but like Yahtzee, it adds enough skill to make you feel like it's not just a mindless exercise. To its credit, though, it is completely unlike Yahtzee (although, perhaps not surprisingly, it is apparently based on a real dice game), giving it a nice, original feel.
The rules for Zilch are pretty straightforward. You roll six dice, and then score some or all of the resulting dice. You can score any number of ones or fives at a time, or three or more of any die; there are also a couple of special combinations (like a 1-6 run or three pairs). After scoring, you can elect to bank or roll again. If you bank, your turn ends, and all the points you have scored that turn are added to your score. (You can only bank, however, if you've already scored at least 300 points.) If you choose to roll again, you can try to score more points. However, you don't reroll dice that you've already used to score. (That is, if on your first roll, you score a single one, you then only roll five dice on your next roll, which obviously decreases your scoring opportunities. If you manage to score with all six dice, then you can reroll all of them.) If you happen to take a reroll and fail to score anything, you zilch! Zilching causes you to lose all of the points that you've accumulated that turn, and, should you be unfortunate to zilch three times in a row, you'll lose 500 points. So, there's a natural balance between wanting to push your luck to eke a few more points out of of your turn and quitting while you're ahead, which makes for a sound tactical foundation for the game. Once one player reaches 10000 points, the other player has one turn to try to beat that, and then a winner is declared.
That's pretty much all there is to the game. The game offers three different AIs (you can also play a hotseat 2-player game) -- Reckless is very aggressive (as you might guess from the name), and so will occasionally pull out huge scores but more often take completely avoidable zilches; Cautious is (again, as you might guess) more conservative, while Realist tries to take the most "human-like" approach. Realist is pretty tough to beat, but even it makes baffling decisions sometimes. The game is well-suited to being a laptop game, since it doesn't demand constant attention, a single round doesn't take very much time, and it can be played entirely with the keyboard. (I should take this moment to mention one poor interface decision, though. When you roll the dice, the scoring options are displayed, and you might think those are your choices. However, in some cases only the highest-scoring option is displayed. For instance, if you roll two ones, only the two ones scoring option will be displayed -- it doesn't appear you can just score a single one, which you might want to do to leave more dice free for your next roll. You can, however, score just the single one by clicking on the die, rather than the scoring option. This parenthetical remark will probably make no sense if you haven't actually played the game, but if you try it you'll see what I'm talking about.)
The graphics are pretty straightforward, but are charmingly carried out, giving the game a pleasing look. There's no music, and the sound effects are basic but well-chosen, making the game pleasant to play. With its default settings, the game does kind of proceed rather slowly, but you can speed it up by reducing some of the dead time.
OK, two rants now. First, a supportive rant. There's an amazing number of comments complaining that the game is rigged (i.e., the CPU somehow magically gets better rolls). These comments could practically serve for a case study in confirmation bias. It's pretty obvious to me that the rolls are fair, but, for instance, when you play Reckless, he occasionally will get phenomenal scores thanks to his aggressiveness. People will look at this and somehow think that the game is rigged, when in fact they're just not noticing all of the zilches that Reckless' recklessness get him, too. There are, of course, times when you will get blown out of the water due to the computer having good luck (I played one game when the computer rolled six ones, an 8000-point roll), but these are balanced out by the times when you get loads of points while the computer struggles. Anyway, my point is, people saying the game is rigged are clearly not paying attention.
Now, an annoyed rant. Zilch features 120 achievements, which is a truly staggering number, and I was terrified that Kongregate would make it an impossible badge to get all of them, which would have been unbelievably tedious. Thankfully, they chose the more sensible route of requiring 100 achivements, and making it only a hard badge. This is because the achievements are simply not well designed. Some of them just require mind-boggling time investments (completing a very large number of games, or scoring a total of a large number of points), or incredible luck (scoring a nearly impossible number of points in a single turn), which is not fun to anyone. Worse, though, is that a lot of the achievements overlap significantly. For instance, there's an achievement for playing a game that lasts 30 turns. There's also one for winning a game that lasts 30 turns. What's the point of the former when you have the latter? I could cite bunches more of examples, but if you play the game you'll see what I mean (you'll also see that, annoyingly, the game doesn't tell you how to get the achievements, which I've ranted about before). This means that the overall achievement count is kind of padded, because of all of the redundancies. Contrast Zilch's achivements with, say, Amorphous+, and you'll see what I mean. Amorphous+ has a lot more oddball, one-off achievements for silly things, so that there's a lot more variety in getting them all. And even though there is some redundancy, the redundant achievements aren't useless -- getting achievements can unlock rewards, which you may find necessary to get the harder achievements anyway. In Zilch, on the other hand, the achievements don't serve any purpose. Overall, I feel that the game probably would be served with fewer achievements, but more judiciously chosen ones.
Anyway, Zilch is a fun game. If you're playing it for the badges, you're probably going to have to play it a little more than ideal -- it's best played in small doses, since the gameplay doesn't change very much, playing ten games in a row can be kind of boring. Still, it's a good design and a good execution, and a fun game to play here and there.