sentences:  Yamauchi also cited difficulty in designing the game for the PSP Go.As the Go features a relocated analog nub, the developers had to make adjustments to ensure the experience felt the same as with a standard PSP.Polyphony Digital's busy schedule with releases of "Gran Turismo 4", "Tourist Trophy", "Gran Turismo HD", and "Gran Turismo 5 Prologue" also slowed "Gran Turismo"'s development.