Sub Commander is a free, independently developed roguelike submarine simulator with an emphasis on realism and freedom of choice. Originally, the game was envisioned to be a kind of cross between Dwarf Fortress and the film K-19 The Widowmaker but it is rapidly growing to a full featured submarine warfare simulator. Eventually I plan to simulate all aspects of cold war era naval and aerial combat, so the player's submarine will be in the midst of a dynamic, procedurally generated global war.
One of the main focuses of the game is dealing with accidents and emergencies aboard the submarine. Nuclear submarines are hugely complicated pieces of equipment and there's a lot which can go wrong - fires, flooding, radiation leaks, lack of oxygen etc are all accurately simulated. Careful management of the crew and the submarine's automated systems is essential to conquer these threats and complete your mission successfully. In some ways, it's like a much more complex version of Faster Than Light aboard a submarine (without the fancy graphics unfortunately!)
While the simulation of the onboard systems is highly detailed, I have tried to ensure the game is accessible to almost anyone and the learning curve is not too steep. The graphics are very basic but I try to keep them clean and functional - but I admit great graphics were never a priority for this game.