I notice something on the wall and it takes my brain out of the zone. Just like in meditation, thoughts are to be let go of, so it is in DDR. Then I start missing steps and losing my flow. I know it immediately, too - Immediate feedback. It's really true with any video game, but with DDR, the entire body is engaged, so my entire body has to stay in the fluidness and spontenaiety of alpha state. I move and flow with the rhythm, and I do well. If I am constantly getting tired or sore, my mind is getting distracted because my body is in pain.
It trains the body and mind nicely. Typically, choosing songs with a bpm of around 120-140 is best, something that definitely keeps my heart rate up, but is not so vigorous that it is hard to physically and mentally keep up with the notes. The idea is something that is invigorating, yet sustainable.
Most importantly, though, it trains the body and mind in tandem. It takes a momentary pulse across the synapses to send the signal - which direction the arrow is pointing - to the rest of the body, to reorient itself for the next step. This game trains an entire mind-body connection.
Training the body, too, is so essential for magic. Our bodies are the vessels through which our energy flows, and when the body works better, the mind works better. When we are physically feeling well, we are more mentally clear and alert.