[ubuntu] Is it possible for me editing the Ubuntu's default theme?

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http://ubuntuforums.org – As title. Currently I'm using 12.04 Pangolin and I like the Ambience theme. But I do hope to make the Bar and Window's frame to be an absolutely black Is there anyway to do that? Please guide me or show me the URL ... thank you. PS: 12.04 Pangolin is the first Ubuntu that I used more than 5 months Previously, I'm with 10.04 Lucid ... but it was last not more than 1 month. (Hardware)