Episode 4 is all about one of the most powerful tools in Modulus that players often underuse: the Efficiency View.
Unlocked through the tech tree, the Efficiency View is accessed by pressing H. It recolours every operator in your factory to reflect its current efficiency, green means running at full capacity, yellow means underperforming, and red means something is seriously wrong. The goal is simple: get everything green. (Side note if you look closely everything also has a pattern on displaying the corresponding number in the key. This is so that those with red/green colour blindness can still see bottlenecks in this mode)
But knowing something is wrong and knowing where it's wrong are two different things. David's approach to debugging uses scrappers as a diagnostic tool. The logic is straightforward; by placing a scrapper at a point in your production line, you relieve the downstream pressure on everything upstream. If your operators turn green once the scrapper is placed, you know the problem lies further down the line, not where you were looking.
Working through a production line step by step, David places a scrapper, checks whether upstream operators improve, removes it, and moves further downstream until the problem reveals itself. In his example, two Cutters were outputting 30 items per minute each, but one of them was feeding into a machine that could only accept 15 per minute. The result was a blockage, invisible at a glance, but immediately obvious once the scrapper technique isolated it. The fix was simple: add a splitter and double the downstream operation.
The lesson is an important one. Even a green operator in the Efficiency View can be hiding a problem, if it's outputting at capacity but that output is backed up, the real issue is with whatever comes next. The Efficiency View tells you where to look; scrappers tell you where to stop looking.
Episode 5 tackles a challenge that almost every player hits as their factory scales: how do you efficiently feed multiple operators from a single belt?
David uses the dye mixer as his example, an operator that takes in 7.5 units of oil and 7.5 units of pigment per minute. Early on, one mixer is plenty. But as your production grows and you're pushing 30 units per minute down a belt, you suddenly need four mixers running in parallel to consume it all. The question is how to route everything cleanly.
He walks through three approaches, each suited to different situations.
The first is the angular approach: one resource flows in vertically, the other horizontally. Resources are split off as they pass each machine. It takes up space, but it's easy to read and easy to debug, you always know which belt carries which resource.
The second is the sequential splitter approach, and it's the most elegant. Rather than trying to divide the belt evenly upfront, you simply run the belt past each machine and let splitters do the work. When a machine is running slowly and its input is backed up, the splitter automatically redirects excess items forward to the next machine in line. No manual balancing required. As David demonstrates, 30 oil per minute feeding four dye mixers (each consuming 7.5) is handled perfectly, each machine takes what it needs, and the remainder flows on to the next.
The outputs are collected cleanly via a tunnel running underneath the row of machines, bringing everything back to a single belt. Two resources in, one resource out; compact, readable, and easy to duplicate if you need to scale up further.
The third approach compresses the layout vertically for tighter spaces, using the same splitter logic but configured for narrow corridors rather than open floor space. Same principle, smaller footprint.
The key insight across all three approaches is that splitters in Modulus are smarter than they look. They don't force an even 50/50 split, if one output is blocked, the flow automatically redirects to the other. Understanding this behaviour is what makes clean, scalable resource distribution possible.
That's your Episodes 4 and 5 catch-up! Make sure you're following us on Steam so you don't miss the next one.
And while you're putting those tips to work...
This time we have a theme: the Free Build Map. We want to see your best builds in the new map, so get building and show us what you've created.
To enter, upload your screenshot to the Steam Community Hub, the screenshot forum on our Discord, or both for a double entry into the prize draw. Please note that screenshots of the pause menu or main title screen won't be counted, we want to see your factories in all their glory!
See you on the factory floor.
— Team Happy Volcano