Minecraft 1.4 [ Prerelease 5 ] 12w39a - JKoop

So here is the 12w39a changelog:

1)Lighting system overhauled.
2)Lots of blocks interact correctly with lighting now (stairs, slabs)
3)Few sound tweaks
4)Fixed witch being white for some
5)More bugfixes & slight tweaks!
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INSTALL INSTRUCTIONS
Windows-

1. Type %appdata% in the search bar

2. .minecraft/bin

3. Drag/Copy the new minecraft.jar file into /bin folder and replace it.

4. Make a new folder named "server" .minecraft/server in that folder drag/copy the minecraft_server.jar file

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MAC -

1. goto Finder/User/Library/Application Support/minecraft

2. FOLLOW STEPS 2-4 above.

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