Minecraft wiki entry for Development, associated text: Additions
Added a thin black block selection outline.
Pressing Esc now opens the pause menu, with options to return to game, generate a new level and save/load level, the last of which doesn't do anything.
Changes
Game ratio is now 854×480, not 640×480.
The block being used is once again shown in the top right corner
Made swimming and sinking faster than before.
Holding the jump key no longer allows for autojumping.
Jump height reduced back to just over 1 block instead of just over 1.5 blocks.
This is the earliest version in the launcher where holding down R no longer causes the player to cycle between different locations - holding the key now has the same effect as simply pressing it.
Lava is no longer transparent and has a thick, red mist when underneath it.
Changed the texture of saplings from to .
The generated world is now completely flat. When generating a new level from the pause menu, the world will be of a long shape (512x64x32), but still flat. It is worth noting that caves can still generate in these worlds.
Trivia
This is the version available in the launcher, added to it among several other versions on August 6, 2013.