hereafter next in step s 9 a paint processing for object flame is performed by the first display mode or the second display mode namely the flame image data to be stored in flame buffer 18 is read out and output on the monitor 19 as a game picture of one flame size then in step 10 it is judged weather the display processing of the game picture is finished if it is judged that the processing is continued step s 10 no steps after s 1 are repeated if it is judged that the processing is finished step s 10 yes the process in fig3 is finalized as described above in the process of fig3 the switching from the first display mode to the second display mode or from the second display mode to the first display mode is performed if the whole processing scale expands and it becomes impossible to catch up the paint processing then the second display mode which requires lighter load for paint processing is settled on the other hand if the whole processing scale shrinks and there is an enough margin for paint processing the first display mode which provides with a better picture quality is applied accordingly the disorder of the picture displayed on the monitor 19 can be prevented beforehand and a high quality picture can be realized although the case where the invention.