I like SciFi. I want to make a SciFi game in space. What do people do in SciFi games?

I got all the basics i.e. gas system (moves with presure gradient)(includes air) fire system (uses up fuil such as some gasses, those gasses can be ignited with sparks and stuff), computers (almost), and a few more things (see http://games.byond.com/hub/Atomixkid/Chain_Reaction ).

I need help. What kindda stuff should the player be able to do? I need ideas, please help.