Java Edition Alpha

Alpha (Survival) is the most recent version of Infdev, that includes new updates such as Redstone and Stair blocks. It is playable both with a downloadable client and at www.minecraft.net/game/ (note: You must buy the game to play)  Attempting to load an Alpha map into infdev (if it includes stairs) will cause it to crash. Infdev levels that were saved earlier can be loaded into Alpha with no problem, and save files from Alpha can be loaded into the infdev preview tool even if they contain new block types.

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. Although this remains the only version linked to by the official website, old development versions can currently still be accessed here (Indev) and here (Infdev), until they are taken down at a later date (presumably when Minecraft Beta arrives).

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.

Current
Since the release of Alpha, the following features were added on top of Infdev's base:
 * 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 this is only private.
 * The addition of Snowy and Icy terrain, plus craftable snow blocks.
 * The addition of Boats.
 * Cow and Slime mobs.

Upcoming

 * More mob types (Chickens and Prefix Mobs).
 * 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 the forums how gameplay will turn out once the mode is released. Speculated features include:
 * Player vs. Player (PvP) - Players will be able to damage one another through attacks and many people will pursue this route exclusively.
 * Raiding - Defense is a critical part to any base in SMP as other players are expected to band together to form raiding parties to destroy and loot player's bases.
 * Community Building - Towns will emerge as players decide to work together. This may either be due to wanting to build with friends or desiring to increase survivability from mobs and aggressive players by staying under the protection of a community.
 * Outposts - After the server has been up for some time, players will start building defenses and lookouts for new players who join the server (Will provide temporary defense while they travel to the player village/town).
 * Cave Cities - Smart servers will build their main town and traveling system underground in either a player made cave or a randomly generated one while having a secondary village above ground which anyone can access. (Like a guest area)

Version History
See patch history.