OOOH! I had an idea of the possibility of my PC dependency, so I checked it out and it was so.
The cause was that the frame rate was about 120.
When I limited it to 60 and played it, it now takes about a minute to catch an angelic fish.
(I was very impressed with how long I could listen to the music and how rhythmic the active action was !!!!)
The difficulty level was, of course, made easier to play!