on error goto *f
    DIM A%(8)
    DIM D(430)
    D=10 
    E=420
    CD PLAY 2
*A  FOR D=20 TO 430 STEP 10
    CDSTAT A%
    IF A%(1)<>1 GOTO *B
    DSP ON "テキスト26",(D,400)
    NEXT D
*C  FOR E=430 TO 20 STEP -10
    DSP ON "テキスト26",(E,400)
    NEXT E
    GOTO *A
*B  END
*f  resume *b