Ziro ($10, free demo) is a fun, casual, puzzle game which includes, for no adequately explained reason, occasional preachy "tips" about global warming. Oddly, none of these includes "turn off your computer." There's something on vendor Kokakiki's Web site about snowmen guardians taking you on a journey, but none of this really factors into the gameplay. Fortunately, that doesn't matter, because the gameplay is clean, fun, and challenging in its own right--no backstory needed.
Ziro follows the usual pattern of problem-solving games: You begin with a simple rule, then you add a second rule, then some variants, then more, and so on. In this case, the basic rules are: You can add two dice together by dragging them on top of each other; adding two identical dice will cause both to disappear. Clear all the dice, you win! Dice can be slid horizontally or vertically, and will slide in the chosen direction until they reach the edge of the map or are blocked by a wall or another die. It's easy to get a die in a position where it can only slide helplessly between two points, unable to rejoin its fellows. Avoiding this dire fate is where the "puzzle solving" comes in.
In addition to the basic dice, Ziro introduces special types. These don't need to be removed to solve the game, but offer new possibilities to the puzzles. Some are dice which can be moved only once, and then "stick," dice which can be moved anywhere and destroyed if needed, dice which are "teleport" gates, dice which can match any die, and many other types. These allow for a lot of variation in puzzles and many levels of difficulty.
Ziro offers some intriguing puzzles, many with multiple solutions. Depending on the puzzle, you can sometimes find yourself in an irrecoverable position with one wrong move; other puzzles are more forgiving. There are three modes of play: "Quest," "Skill," and "Practice." "Quest" mode takes you to various sites around the world, where you play a short series of puzzles with no penalty for restarting or bonuses for smart thinking, whereas "Skill" mode gives you only three lives ("Restarts"), rewards superior play, and offers special bonus dice as rewards or power-ups.
Some of Ziro's puzzles are extremely easy, and in "Quest" mode these can appear even after you've done several levels and clearly have learned what you're doing. Others are much trickier and can stump you until you have that wonderful "Aha!" moment and the entire solution falls into place.
Ziro has a somewhat retro, almost 8-bit, feel to it, especially the background music, which is harshly electronic and "beepy." On the plus side, it was easy to turn off. Some nice sparkles and particle effects liven things up, but a puzzle game is about the puzzles, not about the bling. Ziro provides decent challenge and variety, with a very low price.