Wube just announced that update 2.1 will be Factorio's final content patch. Eight months in development, dropping in experimental at the end of June, stable by summer's end — and then the studio moves on to new projects. If you're like most of us, that news made you do one thing: fire up your dustiest save to see how far that megabase ever got.

Welcome back. Your old friends the biters are waiting. And there's a very good chance that everything you remember about "managing" them is wrong.

The pollution and evolution system is the single most misunderstood mechanic in Factorio. People pour concrete in a 200-tile radius, build six layers of walls, plant trees like they're saving the rainforest — and then act shocked when behemoths show up. Meanwhile someone with a bare wall and a turret line is running a 1k SPM base just fine. The difference isn't skill. It's understanding what the numbers actually do.

Here are the five that matter.

This is the lie everyone tells themselves. "I'll plant trees to absorb pollution and slow evolution." No. The evolution factor isn't fed by how much pollution is on the map. It's fed by how much pollution your machines create, tick by tick. The trees can soak up every last cloud and your evolution still climbs at the same rate, because the contribution happened the moment your boiler emitted the PU.

What absorbing pollution does change: how often biters attack. Spawners gobble pollution as fuel for raids — every chunk over 20 pollution feeds them at a rate of 20 + 0.01 × chunk pollution every 64 ticks. Drown them in clouds and you'll see raids constantly. Choke the pollution off near the border and you'll see way fewer waves, even if your evolution is the same.

That's a huge distinction. Containing pollution buys you peace, not easier biters.

Per the engine defaults:

Translate that. One hour of doing absolutely nothing adds about 0.014 to your evolution. Producing 1 million PU adds 0.015. Clearing a small nest of 7 spawners? 0.014. They're roughly the same magnitude per hour of normal play — until you start aggressively bulldozing nests with tanks or spidertrons. Then spawner kills run away with the lead.

The practical takeaway: don't blitz nests in the early game just because you can. Every spawner you nuke at 0.1 evolution shoves the curve harder than three hours of running your factory. Take what you need for breathing room. Leave the rest until you've got armor-piercing ammo and uranium.

The raw sum from those three sources gets squashed through evolution = total / (1 + total). So if your raw evolution adds up to 1, your actual evolution is 0.5. If it adds up to 9, you're at 0.9. Going from 0.9 to 0.95 takes ten times as much raw input as going from 0 to 0.5.

This is why your first six hours feel like the difficulty doubles every session and then somehow plateaus. It does. The curve is brutal early and merciful late. A lot of players quit megabasing because they assume biters will keep scaling forever. They don't. Once you hit ~0.9, you're basically locked in at "behemoths and spitters, forever," and the system effectively stops punishing you for new factory growth.

Here's the kindness inside the cruelty: that +0.002 per spawner is the raw contribution. After the asymptote squash, the actual evolution increase from killing a spawner at 0.0 evolution is about 0.002. At 0.5 evolution? About 0.0005. At 0.8? About 0.00008.

In plain English: clearing nests in the late game is almost free. You'll meet players who treat the inner perimeter like sacred ground until hour 80, and you'll meet players who've been carving out artillery range since hour 30 and are running fine. Both work — but if you're sitting on a stable green base at evolution 0.7+, you have permission to expand. The math says go.

At evolution 0, spawners produce a biter every 6 seconds. At evolution 1.0, every 2.5 seconds. That's a 2.4× speedup across the whole game — not 10×, not 100×. The reason endgame attacks feel nightmarish isn't because more biters are being produced; it's the unit composition (behemoths replacing medium) and the pollution feeding into spawn pools. The factory itself is the throttle.

If you're tired of getting steamrolled, the answer isn't to "stop polluting." It's to reduce pollution reaching the spawners — solar coverage, efficiency modules near the perimeter, electric furnaces where you can afford them. Cut the supply of fuel and the raids dry up regardless of what the evolution number says.

Three things, in order:

Stop building walls of trees. They don't help with the thing you think they help with. They help with raid frequency, which is real but separate.

Treat spawner kills as a budget. In the first 10 hours, aim for "just enough to expand pleasantly." In hour 40+, swing the axe freely because the cost has collapsed.

Pick efficiency modules over solar-only for your border outposts. A single Efficiency Module 3 cuts a machine's pollution output by 80%. That's production-side reduction — the only kind that matters for evolution.

This is the kind of system design that rewards reading the manual instead of grinding harder, which is honestly the whole reason the factory genre exists. If you nerd out on this stuff, our take on the math behind idle games covers a lot of the same ideas in a different shape — asymptotic curves, why difficulty feels exponential when it's actually softening, all of it.

Anyway. 2.1 ships this summer, and most of the people coming back are going to die to medium biters they thought they were prepared for. Don't be one of them. The biters haven't changed. The math hasn't changed. The only thing that's about to change is how seriously you take it.

See you on Friday for The Conveyor Belt.

The Assembly Line is published by Manu Games — makers of Manu Idle, a peaceful idle RPG for iPhone, iPad & Mac. Learn more →

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