Java Edition Alpha

Alpha (Survival) is the most recent version Minecraft, and replaces older developments versions such as Indev and Infdev. It is playable both with a downloadable client and at http://www.minecraft.net/game/ (note: You must buy the game to play, however while the game is at the Alpha stage of development, it is being sold at a 50% discount for 9.95€ (normal price 20.00€). The price will increase when the game enters Beta.)

Development
Minecraft Alpha is a renamed and merged version of the Infdev and Indev development branches, signalling a progression towards the upcoming beta. The renamed versions were announced by Notch on 28th June 2010, renaming Creative mode to Classic, and replacing the existing 'in development' modes with a single version. This remains the only version linked to by the official website.

The game is updated very frequently, due to Notch working full-time on the Minecraft project since 29th May 2010. Bug fixes and tweaks can happen throughout the week, appearing on the game's development blog, with major additions and changes appearing in 'Seecret' Friday updates, leaving the game's players to discover the included new features. And while the game is playable and relatively stable, there are a few known bugs.

Current
Since the release of Alpha, the following features were added on top of Infdev's base: In alpha there are four difficulties:
 * The addition of Redstone circuits, a logical I/O system including switches.
 * Improved AI pathfinding and spawning.
 * New sounds for caves and mobs.
 * Survival Multiplayer Mode (SMP). Currently, the only way to connect to a server is to find out the IP of it to connect. Here is an SMP List.
 * The addition of Snowy and Icy terrain, plus craftable snow blocks.
 * The addition of Boats.
 * Cow, slimes, and chickens mobs.
 * New music.
 * More paintings
 * Current Height: 128 from bottom to top
 * Press F1 to remove the inventory display and the player's arm (the HUD, or Head Up Display)
 * While holding down F1, press F2 to take a screenshot. The images are saved in %appdata%\.minecraft\screenshots
 * Peaceful - No enemy mobs spawn, falling damage is reduced, health regenerates over time.
 * Easy - Enemies do less damage than normal.
 * Normal - The game functions as intended.
 * Hard - Enemies do more damage than normal.
 * The Nether - A realm with blocks otherwise unobtainable in the normal world. It also features mobs that cannot be found in the normal world.
 * Biomes - Different environments that differ as location/chunk/temperature changes

Upcoming

 * More mob types
 * More block types

Multiplayer
Survival Multiplayer (SMP) is a game mode currently in development that is highly anticipated by the community. Many players have speculated on how gameplay will turn out once the mode is released. Speculated gameplay highlights include Player vs. Player (PvP), raiding parties, base defense mechanisms, and cooperative player towns. A few clans have been formed for SMP.

Currently, the new game mode is under heavy construction and is very buggy. More information can be found on the Known Survival Multiplayer Issues page.

Originally, Notch has allowed several people from the Minecraft IRC channel to participate in the first tests of Multiplayer. The first tests were private. Notch then allowed invitees to invite other people; however the password was leaked and the server was quickly filled up. After that, anyone could get into the test server (when it was online) by typing a password that was shown on the multiplayer screen.

Notch released the first version of the server software on the 4th of August, 2010. The client was updated so that players could enter the IP of a server to join it. As of 10 September 2010, SMP now finally has a server side inventory, signs and chests. Furnaces have also been fixed to work almost correctly. However, Notch said it wasn't secure yet.

Version History
See patch history.