Base game
Star Fleet II: Krellan Commander is a complex and detailed space war simulation. Starting with just a single Krellan battlecruiser, as you rise in the game's seven ranks (each rank has five missions), you'll gain more complexity, such as escorts, planetary invasions, and eventually full sector command. Each mission is a randomly-generated galactic war sandbox, and while you have specific objectives, how you accomplish them is entirely up to you. No other space game gives you this much depth, detail and control. Fight, board, and capture ships, send landing parties and full invasion forces down to planets. Bombard cities (sparingly, as you want as many cities intact as possible) from orbit while avoiding planetary defense fire from high technology planets. It's all here.