Unlike many other action RPGs done in this style, Space Siege is a very active game. It's almost RTS-like in the way it rewards the ability to rapidly click on just the right enemy or immediately use the best hotkey for a situation. There are a few "boss fights" where it's perfectly possible to wipe out even if you have adequate healing packs and a good loadout of skill and equipments. One of these major battles occurs within the first level, after a series of intense cut scenes. The producer at the demo was quick to stress that the density of cut scenes in the early game wasn't representative; most of the story would be told by items that had to be found in the course of the game, like voice recordings, diaries, and particular NPC interactions.

Instead of amassing gold, you amass parts from defeated enemies. Your protagonist is an engineer, and so he can use these spare parts to level up HR-V, his handy companion robot, or to improve his own weapons. It is feasible to invest so much in HR-V that you spend most of the game letting him do a lot of the fighting for you, while you stand back and take potshots at enemies or spam skills. HR-V and the protagonist have separate HP bars, and it seems easy to make HR-V into something that can easily soak up colossal amounts of damage.

Save rooms, on top of auto-saving progress, also let you purchase new weapons, install cybernetics, and restore your and HR-V's health to maximum levels. While using hotkeys was much faster, you could also pull up your maps, skill trees, and other important menu screens with a click of the mouse. This is not really an advisable play style, since how rapidly you click onto enemies or use skills can make a life-or-death difference in combat. You need to acclimate yourself to the hotkeys as quickly as possible, and make sure your best items and abilities are mapped to the hotkeys you like the most.​