Aurora is a freeware, 4X space simulation game, designed by Steve Walmsley and released in 2004. Difficult to learn and slow to play, this is a game well-suited to people who like deep strategy and don't mind poor UI. It is constantly being updated and the latest version is v1.12.1 C#.
Originally just a simple program to augment pen and paper game, known as StarFire, space battles and role-playing, it has since evolved to something more, with the game being playable with the addition of AI, and many other features.
Aurora allows the player to create a procedurally generated galaxy, consisting of detailed, accurately scaled star systems connected to each other via jump points. A player starts off as a space faring nation, discovering the secrets of Trans-Newtonian technology and uses it to expand and create an interstellar empire. Aurora is a sandbox game, with no goals, but nearly every setting can be edited in a designer mode for creating custom scenarios. The game is played in increments, where time is advanced from between 5 seconds to 30 days as chosen by the player. So it is a mix between real-time and turn based gameplay.
The game takes great attention to detail, with vast star systems many billions of kilometers wide across along with orbiting planets, moons, asteroids and secondary stars. The game also has a complex combat system, with minor stats such as radar resolution, missile tracking speed, turret rotation speed and custom, programmable missiles all playing vital roles in battle. The game also comes with a fully functioning private economy with private freighters and colony ships carrying goods and colonists between your planets.