Hi there! It is always hard to determine whether the object of infatuation has any genuine interest in you. I have been there many times. It is such euphoria that you honestly don't know what is going on.
Infatuation is a confusing thing. Any little thing that the other person may do convinces you that they like you.
When he smiled at you and acted kind of playful when you were on the computers, he may have been flirting a little bit. Do you ever talk? If you are best friends, then it may have just been friendly, but if you do not talk very often, then chances are that he shows some interest in you.
You two are only in 7th grade. In many cases, you are not mature enough to have a relationship. There definitely are exceptions though. If you think that you are mature enough to be in a relationship, then you should definitely try. Hope for the best, but prepare for the worst.
You maybe should wait a little while before doing anything major. You still are a little young to be getting into relationships. This is up to you though.
Try going up to him, and strike up a conversation. You could ask about classes, or something that relates to your modern day lives. Try to act customary, but maybe a little flirty to give him a little hint that you like him. See how he acts. If he says or does anything flirty, then he probably has some interest in you.
Just do this for a few days. You can't just expect to talk once and don't do it again. Just take it one day at a time and see how everything goes.
In conclusion, just talk to him in a little while and see how things are going with him. Don't take it all too fast, or things may fall apart. Hope for the best, but prepare for the worst. If you want to talk with me, you can e-mail me at im_with_stupid@golivewire.com. I will get back to you as soon as I can. Good luck with your problem!!
-Chris-