sentences:  Creator Kazunori Yamanuchi was against the idea of using external controllers via PSP Plus for more accurate control, telling an interviewer "if you want to play on "Gran Turismo" using a PS3 controller, you will have to play on "Gran Turismo 5"".Fitting a full-scale "Gran Turismo" on the PSP platform was a challenge for Polyphony Digital.Series director Kazunori Yamauchi stated that the main problem was trying to fit the game in such a small memory space.