Lots of chord changes
Its based on the circle of fifths: a technique for playing all 12 keys in succession in a natural sounding way. You start in any key and then move up a fifth and just carry on like this. So starting in the key of A the sequence is A - E - B - F# - Db - Ab - Eb - Bb - F - C - G - D and back to A
Its great fun to play: like having 12 mini-songs in a single piece
Go on have a go!