Sins II Dev Journal: v1.65 'ARES: God of War' Preview
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Welcome to this Dev Diary! I’m Tom Fortune, one of the engineers on Sins of a Solar Empire II, and I’ll be walking you through the reasoning and motivations behind the upcoming AI overhaul. Let’s get started.
Cause & Effect
If you've spent some serious time playing against the Sins II AI, you likely already know the shape of the general complaints we get. The AI doesn’t really like to fight as much as we’d like. It builds a credible early empire and then has issues maintaining it. It spends wildly and in ways that don’t necessarily make sense. You show up to a planet, and structures and items are not built in a way a human would ever do. Fleets get distributed a bit strangely. Exotic factories rarely get built, research wanders instead of compounding. At higher difficulties, the answer to "make it harder" has historically been more resources rather than smarter decisions, which feels less like a stronger opponent and more like a tax.
None of this is for lack of effort. The existing AI is a layered system of specialist controllers: One for purchasing, one for fleets, one for colonization, one for research, one for defense, and several more. Each makes locally reasonable decisions on its own. That architecture has carried Sins II from launch through every expansion, and it does an enormous amount of work that players never see: keeping economies solvent, keeping fleets supplied, keeping planets defended, reacting to threats. The reason it struggles in the late game isn't that any one controller is broken. It's that there has never been a layer above the controllers whose job is to look at the whole board, decide what the AI is actually trying to accomplish, and then make the controllers cooperate toward that plan. Until now, each controller optimized its own little kingdom without strong coordination.
Introducing ARES
After more than a year of fixing symptoms, last December we decided to bite this rather large bullet and fix the cause. Rather than patch each controller into being more aggressive or more focused in isolation, we wanted to introduce a single strategic brain that owns the AI's intent for the match; and then have the existing controllers execute that intent.
The controllers are very good at how. They've never had much of a why. So, we created a top layer to sit above all of them, the Adaptive Reasoning & Execution System, or ARES for short. ARES is now our why.
Three principles drove the design:
ARES is a director, not a suggester.
When ARES is enabled, its decisions are orders. Controllers don't get to quietly re-evaluate them or fall back to their old autonomous behavior when ARES says something inconvenient. If ARES picks a target, fleets go there. If ARES says the economy needs a refinery world, the planet controller builds toward a refinery.
Strategy is goal-shaped, not rule-shaped.
Instead of a thousand if/then statements describing what the AI should do in every situation, ARES generates and scores a list of candidate goals: capture this territory, defend this border planet, build a capital ship for your fleet, rush this tech tier. Basically, instead of a behavior tree branch that says ‘if enemy fleet > my fleet, then retreat,' ARES asks 'Is continuing this goal still worth more than the alternatives?’
It will commit for as long as those goals remain the best option. Goals are concrete things with a target, a cost, a chance of success, and a payoff. That makes them tunable and inspectable in a way that hand-written behavior trees aren't.
Difficulty should mean better thinking, not bigger numbers.
Higher difficulty AIs should see the board more clearly, score targets more accurately, commit to plans more decisively, and tolerate more risk, not just earn 30% more credits. That's a long-term goal and it's not fully realized yet, but the architecture is built for it.
ARES sees the game through a perception filter whose accuracy is data-driven per difficulty level; and its scoring noise, goal-switching inertia, and concurrent-plan caps are all dialed in per difficulty as well. However, this has a caveat: eliminating the AI’s need for cheats does not mean that we won’t give them some anyway. We envision a future of Sins' AI where no difficulty needs cheats, but some may be given anyway to further increase difficulty. In short, impossible truly becomes impossible.
What Makes ARES Tick?
So how does this new layer work? Here's a quick overview of what happens every time ARES thinks:
Perception: Everything ARES learns about the world passes through a per-difficulty perception filter: Fog of war, intel staleness, capability flags for things like, "Can I detect chokepoints?" or, "Can I estimate enemy income?" Lower difficulties see less and guess worse.
World State: ARES rebuilds a single snapshot of where it’s at: Estimated game phase (rough boundaries, not strictly defined), economic phase, peak vs. current income, fleet strength relative to neighbors, supply utilization, attrition, front lines, chokepoints, expansion candidates, per-enemy threat assessments, and which gravity wells border whom.
Engagement Appetite: Based on the world state, ARES decides how aggressive it feels: willingness to commit forces, tolerance for losses, appetite for risk. This number feeds into how it scores its options next.
Goal Planning: ARES scores its candidate goals: Military ("capture this," "defend that," "destroy their fleet") and economic ("expand here," "establish a factory world"); ARES then picks the best ones up to its concurrent-goal caps and commits. Once a goal is active, it persists until completed, abandoned for cause, or dominated by something dramatically better.
Directives: ARES writes orders into a per-domain output bus: Attack directives, defense directives, fleet composition directives, economy directives, research directives, colonize directives, diplomacy directives; and the pre-existing controllers then consume them. Directives are rebuilt every tick; they are guidance, not state. The persistent state lives in the goals.
Feedback: Before scoring next tick's goals, ARES reads back what the controllers couldn't do last tick: Research it couldn't afford, structures blocked by missing infrastructure slots, ships that needed a research subject the AI hadn't unlocked, etc. ARES then folds those signals into the next round of planning. This is what closes the loop. The strategic brain learns from the executors instead of just shouting at them.
The result, is an AI that picks a recognizable plan, commits to it, builds the economy that plan needs, builds the fleet that plan needs, and presses the plan instead of getting distracted. You can tell from watching the map. Fleets converge on real objectives. Defense forms up at the right gravity wells. Research advances along a coherent track. Pressure mounts in one place instead of dribbling everywhere.
What’s Still Being Worked on?
ARES is in the player's hands as an opt-in because it's functional and competitive, not because it's finished.
Here’s an honest list of what we know still needs improvement:
Late-game fleet composition
Capital and super-capital build targets flow through correctly, but the AI is still under-investing in titans and command ships relative to where a strong human player would be by the established and late phases. We want the AI's late-game fleets to look like late-game fleets, not just to be larger early-game ones. Expect updates on this very soon.
Fleet engagement commitment
ARES decides when to attack pretty well, but its in-combat commitment, "Do I press, do I disengage, do I reinforce?", is still leaning on the existing fleet behavior. We have a phase of work planned to bring that decision under ARES as well, so the fleet doesn't break off when ARES wants it to push.
Econ-to-war signaling
Economic state already informs which military goals look attractive, but there are patterns the AI still misses (e.g. recognizing when an enemy's economy is brittle enough to be worth a targeted strike, rather than a frontal assault).
Difficulty as cognition
As discussed, we want difficulty to scale ARES's quality of thought more than its income. Some of this is wired (perception, scoring noise, concurrent goals, re-evaluation cadence), but more difficulty-scaled tuning is still ahead of us.
Team play
ARES is an angry fella. It really struggles to recognize the difference between an ally and an enemy, and in team games, can generate war goals against allies; and wind up getting stuck on an unresolvable goal. This should be resolved, but, keep an eye out!
Tuning, broadly
Every number in ARES - scoring weights, posture thresholds, attrition limits, role templates, goal caps, demand profiles - is data-driven precisely so we can keep tuning during opt-in based on what we see in real games.
Multiplayer
Multiplayer works, however, there are issues with hot-joining at the moment causing desyncs. Do so at your own risk. Everything else: single-player, full multiplayer from the lobby, is fair game.
Conclusion
ARES is going to keep evolving throughout the opt-in period and beyond. We're not shipping this and walking away. We'll be iterating on it in public, based on what you tell us and what we see in our own playtesting. That's the whole point of the opt-in: not for you to play a finished feature, but to help us find the rough edges. The games where ARES felt sharp, the games where it did something baffling, the difficulty that felt miscalibrated, the faction that didn't feel like itself. All of that is gold to us right now.
There's no substitute for real games. If you've got a save or replay where ARES did something especially smart or especially stupid, send it our way, ideally in the Discord.
Thank you for your continued support and we’re eager to get your feedback!