It's interesting how the arrival of a new form of user interface has spawned an entire genre of games. Just as top down strategy games were inconceivable before the 'mouse', tapping games would have been rather weird before the hand-held screen and touch controls. Theme is usually an excuse in a tapping game. In Tap Tap Dash it is also difficult to comprehend.
You are guiding a random critter over suspended platforms, signaling it whenever it needs to turn or jump. Controls are almost nonexistent. All maneuvers are performed in a sequence, the only variable being the timing. So in essence, whether you jump, turn left or right is inconsequential. And that's actually great. Because levels will start speeding up and before you know it, the screen will begin to rotate in weird directions just to confuse you. So in order to be proficient at Tap Tap Dash, you will need disregard the visual aspect as much as possible and focus on the timing of maneuvers exclusively. A rather hard thing to do when you are constantly examining the scene to figure out when you should tap.
If I were to find a merit of Tap Tap Dash (besides it being rather addictive if not frustrating) it would be that of a good early training for fencing. I remember having to catch a falling ruler along a wall. I never did manage to catch it in time, but maybe if I had Tap Tap Dash in 1996 that would have been something less of a problem.