PURPOSE: To remove fatigue of a user's eyes by making recording to eliminate sudden change of brightness at switching of a picture.

CONSTITUTION: When reproduction of a disk proceeds to, for instance, No. 201 and shifts to stationary reproduction in which the first problem is recorded, a user inputs an answer through a keyboard 15. A microcomputer 13 judges whether the answer is correct or mistake, and gives instruction to the disk player 11 to reproduce record lines No.202∼203. Recording is so made in the recording lines that reproduced picture vanishes gradually. The computer 13 gives instruction to the player 11 to reproduce record lines No. 231∼280 or No. 281∼330. The answer of the first problem is recorded in the lines No. 231∼280 from low level brightness to high level, and the second problem is recorded from low level to high level.