AATraders is an online game that is played in a normal Internet Browser. There is nothing to download and any age can play. It has a space theme and you start off in a small space ship and will need to trade with differt space ports to earn credits so that you can upgrade your ship.
Once you create your own planets, you can the buy different space ships and can continue to trade or take a more agressive role and start attacking other players.

Alf's game is a great place to start learning: Alf's AATraders Game