Tony Hawk Underground Pro is almost a total conversion mod for Tony Hawk's Underground 2. It adds tons of features like, more character customization, level creation tools, levels from THUG 1, THPS 1, 2, 3, and 4. And the main feature from all this, it re-adds online to the game! The original GameSpy Servers went down with the company, but OpenSpy, an open source alternative, helps to alleviate the pain. This mod is "the game that most Tony Hawk fans were waiting for." While Tony Hawk HD was a step in the right direction, most Tony Hawk fans believe that THUG 2 was the peak of the engine used in the game. It had great physics and lots of moves to get combos insanely high, like transfers, and flips. To anyone interested, The Official Site can be found HERE.