Since Unity has been introduced in Ubuntu 10.10 Netbook Edition, there have been many changes in it just since 10.10's release. The switch from Mutter to Compiz is one example: Compiz, unlike Mutter, has more animations and other effects that allow some incredible things like autohiding of the Unity Launcher, Launcher transparency, and familiar things like the world-famous desktop cube enabled by other Compiz plugins that can run alongside Unity (also a Compiz plugin).
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