The Art of War tells us that there are five fundamental factors to war: Politics, Weather, Terrain, the Commander, and Doctrine. But the terrain has been largely static in RTS’s.
A new feature of Sins of a Solar Empire II is that all the planets are in active orbits. Their location and the links between them change over time. Because the orbit differs based on how far from the sun the planet is (Mercury orbits our sun much faster than Uranus), formerly cohesive empires can become scattered over time. The process is slow, but it is happening. Orbits can either be prograde or retrograde.
This means that players always need to be evaluating their position on the map. New threats open up as lanes change that connect the player to a planet heavy with pirates, separate a planet from the rest of the player's control, or provide a new route directly to an enemy. It isn’t as simple as creating a turtle system with a massive starbase to block access to the heart of your empire. That may buy you time, but a patient enemy will wait for a better opportunity.
It also means that new opportunities arise over time. Personally, I love getting to an inner world and setting it up with defenses and factories knowing its going to eventually be orbiting through other players' territories and causing havoc. The opposite of a single defensive starbase defending my home planets is having one that orbits into my enemy’s territory and begins blocking them from the rest of the map.
This movement is displayed in game, as well as providing warnings when a new lane will be lost or created. Players' home worlds are at the edges of the system to minimize the impact of orbit changes. The deeper the players go into the system, the more orbits matter. Some players may prefer the stable cycle of the outer planets, and others may rush to control the chaotic inner ring.
Sins has always been a RTS played at 4x speed. The plans the players make take time to pay off; you must carefully balance immediate priorities with long-term goals. The ever-changing map now becomes a part of that equation.