What to do?(Bored during summer)?

Well, im pretty bored during the summer and have nothing to do. I have friends, but most of them are doing things and are busy. I tried playing videogames but those got boring fast. I do have a hobby, which is paintball/airsoft, but that costs a lot of money and that is what I don't have. I also live in a condo and dont have a back or frontyard. Any suggestions? Im 15 by the way.