Your fleet costs more than your economy can sustain. That's the point.
The Outer Line has one resource: Supply. You earn it from asteroids. You spend it on ships, structures, modules, upgrades. When income drops below what your fleet costs to maintain, things go wrong fast. I wanted the economy to be something you feel in every decision, not something you optimize in a spreadsheet.
Why one
I tried multiple resources early in development. Supply for building, a second currency for maintenance. It lasted about a week. Every interesting decision the economy needed to create worked fine with Supply alone. The second resource added complexity without adding depth, made the UI busier, and didn't make a single choice more interesting than it already was.
With one resource, you always know where you stand. One number going up, costs pulling it down. You can read your economic health at a glance and get back to the actual game. A lot of RTS games do interesting things with multi-resource economies, and I respect that. For the kind of tactical decisions I'm building around, simpler felt right.
Asteroids and income
Supply comes from Supply Nodes built on asteroids inside Gravity Wells. Each Gravity Well has different asteroid density: an industrial one might be packed with viable positions, while a frontier outpost barely has a handful. The stockpile is global. It doesn't matter which Gravity Well produces the Supply, everything flows into one pool. I considered local stockpiles with logistics between them, but it felt like busywork. The decisions I want the player making are "where do I expand" and "what do I build", not "do I have enough Supply in this specific Gravity Well to queue a Destroyer."
Mining Stations amplify income from Supply Nodes in the same Gravity Well. They don't produce anything on their own, but in an asteroid-dense Gravity Well the boost adds up fast. Building one means giving up the Major Structure Slot for that Gravity Well, choosing economy over a Military Station or a Shipyard. That choice deserves its own devlog, and it'll get one.
The upkeep squeeze
Every ship you own costs Supply to maintain, every minute it exists. Light ships barely register on the budget. The heavy classes drain noticeably more, and fielding a Dreadnought is an economic commitment that reshapes what you can afford to do with the rest of your fleet.
This means your fleet has a practical ceiling, and it's not the Command Point cap. It's your economy. Build more ships than your income can support and your net Supply goes negative. No new construction while you're in the red. Stay negative long enough and your ships start losing combat effectiveness. The game is telling you: you overextended.
The real question is never "how many ships can I build?" It's always "how many can I keep?" And the answer shifts constantly. Lose a few Supply Nodes to a raid and your comfortable margin vanishes overnight. Take a new Gravity Well with good asteroid density and suddenly you have room to breathe again.
Raiding wins wars
Supply Nodes can be destroyed but not captured. You can't take over the enemy's economic infrastructure. You wreck it, then build your own, and that rebuilding takes time. Gutting someone's economy in a Gravity Well is a wound that lingers.
This makes raiding one of the strongest plays in the mid-game. A fast group of Destroyers jumps into a poorly defended Gravity Well, smashes a few nodes, and jumps out before the main fleet can respond. You didn't kill a single warship. You might have won the game anyway. The enemy's income drops, their fleet starts bleeding upkeep they can no longer cover, and the spiral begins: less income, fewer replacement ships, less ability to defend the remaining nodes.
I've had test games where I won every major engagement but slowly lost the war because the AI kept picking off Supply Nodes in Gravity Wells I couldn't spare ships to protect. Strong fleet, crumbling economy. That's the kind of pressure I hope the game creates consistently, though the numbers are still rough.
Still tuning
Upkeep values need more testing. The Dreadnought is the hardest to get right: expensive enough that fielding one is a real economic event, not so expensive that building one feels like a mistake. The Supply Amplifier module on the Mobile Shipyard adds another variable, letting economy-focused builds sustain larger fleets than combat-focused ones. Whether all of that holds together in practice, I'll find out with more playtesting.