Cons: Mods tend to quit working just about every update
Minecraft is the epitome of an open world sandbox game. You start out dropped randomly into an immense procedurally generated world and you can pretty much do whatever you want. There's no real direction or prodding you forward, except in the limited sense that the tree of achievements is usually a nudge in the right direction. Invariably you will end up building some type of make-shift shelter the first day (or the first night, when you realize monsters come out with the darkness and would like nothing more than to kill you). This usually consists of dirt squares stacked into walls surrounding you to wait out the nights until you can build a more permanent shelter, but a hole dug into the side of a mountain or into the ground works just as well.
The world is made up entirely of blocks or cubes. Dirt, stone, trees, water, lava, diamonds... there are tons of different blocks that comprise the world around you. Blocks can be destroyed, picked up, moved around and reassembled to your heart's content. Plants and animals, even your character (and those around you in multiplayer) are made up of blocks -- many of them animated. It's a rather simple art style, but it's kind of unique and really works wonders in Minecraft. There are also many different texture packs you can download that are created by users and enthusiasts that can change the look of the blocks. I'm a big fan of the LB Photo Realism Pack myself, with the Dokucraft texture pack being a close second. Thankfully you can easily switch between the different texture packs so I can alternate using my favorites and trying out new packs.
You walk around in a first person view, with whatever happens to be in your hand visible -- whether it be a sword, pick, torch, fish or even a block of sand. You can toggle a couple of additional camera angles with the F5 button, including a third-person view and a camera in front of your character. You move with the WASD keys, and can sprint by double tapping W. You can also jump with the space bar, and since the world is very tall you will be jumping a lot as you climb out of caverns, climb up mountains or just navigate around the world.
You start off with nothing but an empty inventory and your bare hands, but you can collect resources and then craft them into objects to help you along. For example, you punch a tree block to destroy it and pick up the wood that falls to the ground after. When you bring up your inventory screen (by pressing I), you are presented with 27 empty item slots, 4 slots for equipment (helmet, armor, leggings and boots), 9 inventory quick slots, and a 4x4 square crafting grid. You can place a piece of wood into the crafting grid to turn it into 4 wooden planks. Take those 4 wooden planks, and place them all in a square to fill up the grid and you can create a crafting table. Place the crafting table somewhere in the world and right click on it, and you're presented with a 6x6 square crafting grid which allows you to make a great variety of different items.
Take 2 of those wooden planks and arrange them one over the other, and it creates a stack of 4 wooden sticks. Take a wooden stick and place 2 stone blocks in a line above it to make a sword. Place 3 planks across the bottom row with 3 pieces of wool above them to make a bed. There are many, many things that you can make with different combinations of the various blocks -- and I'm not just talking about the standard things you would expect to see. You can make a record player or a block that plays a musical note. Boats. Pistons and pressure plates. Mine carts and tracks to use them on. The possibilities are staggering. Just try arranging all kinds of different materials in different patterns and see what you can come up with.
Many of the items you can craft have various versions based on what materials you use to craft them as well. For example, a pick axe may be made of wood, stone, gold, iron, or diamond. Higher quality versions have more durability so they last longer, and they also are quicker at what they do. A diamond pick will last a long time and will tear through stone like nothing, and it also happens to be the only pick of sufficient quality to mine obsidian. Diamonds are rare however, so you wouldn't want to waste them if you were only digging through stone. I usually keep a diamond pick in my inventory along with a pile of stone picks while I'm mining. Stone is abundant, so I just use stone picks to mine stone -- but if I come across some diamonds I can break out the diamond pick to mine them with, as destroying them with a stone pick destroys them completely instead of dropping the diamonds for you to retrieve. There are similarly different quality versions of hoes, shovels, axes, swords, armor, etc.
Not only that, but after creating all these wonderful items you can make use of them in the world as well. Digging deep into the earth, you can uncover rare deposits of gold, diamonds, redstone and other things. Redstone is particularly noteworthy because it can be used as a sort of electrical system in Minecraft; mining the redstone drops redstone dust which is used like wiring when you place it. This is substantial, as it allows insanely complex creations to be made. Like what? Think big... calculators, cannons, elevators, etc. Granted many of these things are complicated to make, take up a lot of space and use a lot of resources in their creation, but that's half the fun.
In addition to the redstone dust that you can use as wiring, there are other pieces that can be crafted to aid in creating complex devices. Switches, levers, pressure plates, buttons, repeaters, and redstone torches themselves which actually provide power. Using the various pieces and blocks, you can create multiplexers, logic gates, circuits, relays and just about anything imaginable. There are countless tutorials on YouTube or the Minecraft Wiki to detail various designs and implementations or give you some ideas.
You have a health bar and a hunger bar. If you lose all of your health you die and lose half your experience, and the other half gets dropped as experience orbs at the place of your death. If you only lose a little health, it will slowly regenerate itself as long as your hunger bar is full. On the flip side, if your hunger bar is empty you will slowly lose health. Eating different foods will fill up your hunger bar by different amounts, and there are many ways to get food. Killing pigs, cows or chickens is a quick and easy way to get pork, beef or chicken. Throwing this meat into a furnace and cooking it before eating makes it heal more of your hunger bar though. You can also fish, plant wheat and harvest it to make bread, or even bake a cake.
The randomly generated world is practically limitless in size. Granted, there's a hard limit, but it's many times the size of the planet Earth if you count each Minecraft block as 1 square meter... which is pretty limitless as far as I'm concerned. You could quite literally if you desired, wander the map for your entire life and probably not manage to explore it all. The world is made up of "chunks", which are generated as you explore, otherwise your hard drive would be entirely filled up with useless area that you would likely never play in. I have created a few different worlds that I play on; one takes up 28MB on my hard drive, another takes up 52MB, and the last one takes up over 1GB of space. The last one, however, is one that I host multiplayer and play with my brothers most of the time, and we've gone off exploring and building massive mine cart tracks connecting each of our towns to each other which is why it is overly large. I don't imagine anyone could have enough hard drive space to fully explore the world, but 20 people could all hop on a multiplayer game and explore all year and it would probably still fit on a common 2TB hard drive.
Minecraft is not all about crafting things and exploring however. The game features day and night cycles, and when night time rolls around hostile creatures spawn in the world who are bent on destroying you. Skeletons, zombies, exploding creepers, spiders... which is why building shelter during the first day is kind of important. They won't spawn on top of you nor will they spawn if there's enough light around, so creating torches and placing them on the walls of your shelter is immensely helpful. After you've got a shelter though, hunting these creatures can be rewarding and helpful. Creatures not only drop common crafting ingredients and experience orbs, but they also rarely drop other items such as picks or bows. You must kill spiders to collect string so that you can make a bow or a fishing rod, for example.
The experience orbs let you "level up" in a way, but not in the traditional sense. Really you just take all of your levels and spend them once you make an enchantment table to enchant your items. Stronger enchantments take more levels to enchant, and using a level 50 enchantment on an item while you are level 50 brings you back down to level 0. Most equipment has a durability or number of uses before it is destroyed however, so I find it best to use low level enchantments on equipment because it's much quicker to replenish a few levels of experience than it is to replenish 50. You lose a lot of experience if you die as well, so saving up 50 levels worth is often difficult to start with. While it only takes 59 experience to get from level 0 to 5, for example, it takes 4625 to get from 0 to 50.
In addition to hostile creatures, there are also docile creatures that you can interact with. Killing cows, for example, can drop pieces of leather or raw beef. You can also use an empty bucket on a cow to milk it, or feed a couple of cows wheat to make them have a baby cow. Pigs, chicken, sheep and squid, there are a number of these creatures that have varying degrees of usefulness -- and more are always being added in updates, or can be added via 3rd party game mods.
Some of the 3rd party mods are pretty simple but really nice, like adding in a mini-map, new items or creatures -- but some are much more complex like allowing you to make your own crafting recipes or adding another entire dimension to the game that you can travel to through a portal. There's even a mod that allows you to build and fly air ships!
Along with the main game world, there is also another area of the game called the Nether, which can be created by lighting a fire in a 4 block wide by 5 block tall obsidian portal frame. The Nether is a hellish area filled with lava and brimstone, zombie pigmen and ghasts that shoot fireballs at you. Every step you take in the Nether is equivalent to 8 steps on the surface, so creating a portal here and traveling a long distance before making another portal back to the surface can allow you to travel a much further distance than you could by surface travel alone. In recent updates fortresses were added in the Nether as well, along with new creatures and items.
There's also one more area to the game, The End, that consists of a large empty area with some obsidian pillars in it and a large dragon flying around overhead. This acts as the "end" of the game and the dragon as the "final boss", though the game never actually ends. Killing the dragon does give you some nifty ending text and scrolling credits before you continue playing though, as well as completing one of the in-game achievements.
There really isn't much in the way of background music in the game. Some light ambient music plays a few times per game "day" that, while good, you really won't notice. You can also craft a jukebox and obtain a number of different records, but they're only a few minutes each and only audible if your character is near by. The sound effects are pretty good, and some of them (like the hiss of a creeper or the groan of a zombie) are downright eerie, and really help with the atmosphere of the game.
Overall Minecraft is one of my favorite games released in the last few years, and it gets a lot of play time around my house. Being so open ended and letting do pretty much whatever you want and build whatever you can imagine, it's like Legos for the soul. Combined with the ability to play with other people online, it makes for an excellent title with a lot of longevity and immense replayability. It's currently priced at a reasonable $26.95, which is less than some other games I've picked up recently that I rarely play.
Minimum system requirements include a Pentium 4 or equivalent processor, 256MB of RAM, an ATI Rage or GeForce 256 video card with OpenGL 1.2 support, 90MB of hard drive space and Java Runtime Environment (JRE) 6 or above. It will probably run a little slow with this setup, especially on 32-bit systems, but it's playable. Minecraft works beautifully in Windows XP, Windows 7, FreeBSD, Linux, and supposedly in Mac OS X. It will likely run on anything since it's written in Java.
Since the Minecraft Server application is a separate program, I set it up my dedicated server so that I could play with my friends and family over the Internet. My dedicated server has a single core 2.6GHz processor with 512MB of RAM and an 80GB hard drive, and it could easily handle the 4 or 5 of us who usually played at the same time. Once in a while the games would crash with an out of memory error, but reconnecting brought us right back into playing again without issue.