My little girl is 2 years 10 months. I think she is quite clever on the whole (knows all the letters and numbers, can count to 30 and do simple maths e.g. there are 4 people in the room, if mummy leaves there will be 3 left etc., does jigsaw puzzles of around 25 pieces). She is also very sociable in that she likes to talk to both adults and children and actively engages other kids in play. Therefore, up until now, I haven't been concerned about anything.
Recently, I've noticed that she is very rigid in her behaviour and how things need to go. For instance, if we are playing with a certain toy on the sofa one day whilst eating a snack, she will not play with that toy the next day unless we sit in the exact same spot on the sofa and eat the exact same snack. If daddy plays a game with her in one corner of the room, she will only play the game with him (not with me) in that exact corner of the room from that point onwards. Etc. Etc.
I've never had a child this age before, so I have no idea whether this is common in toddlers. I know they like routine at this age, but was also thinking it could be indicative of ASD or something along those lines. However, given that she seems to be doing OK developmentally and socially otherwise, that would surprise me.
IABU - this is common toddler behaviour and nothing to worry about
IANBU - this could be indicative of ASD or another developmental issue