I tend to be on the neat (read OCD) side and I will, many times, ask my son to clean up one set of toys before starting a new one. I have seen, in the past, that he will often mix up blocks or other toys of one type with another so I have tried to be more flexible about it. Recently, he made a racetrack of all kinds of different materials, including train tracks, musical instruments, and Bakugon cards. It’s interesting to me how, we as adults, don’t think naturally of mixing things up like this. However, for a 4 year old, there is no apparent barrier to mixing things up.