Played that video game. Really liked that piece. It was time to make a piano version! I done all work by ear, with the help of audacity in which I slowed down the tempo. Reducing tempo causes sound distortion, but still leaves it listenable if not reduced too much.
The original piece starts with only piano. I first thought there were only strings in addition to the piano, but in reality there was also a guitar-like instrument. Notes written in the sheet music are 90% what is in the original piece, but where I had to make much more choices was the notes I had to cut out: Everything can't be played with 2 hands on a piano and also there mustn't be too much notes on one instrument or they will get mixed up and it will sound bad. Chords: they were too large for 2 hands, they just had to be made sound as much the original piece as possible while removing notes to make them playable.
I discussed this with the owners of it's copyright, and they were happy about this.
My piano arrangement: http://www.youtube.com/watch?v=W1FaPT5yxwk