Substructure is a Stardew Valley-inspired factory sim that takes one of Factorio's hardest and best mods and turns it into a dizzying, planet-wide game of its own

Substructure is an attempt to take one of the factory sim genre's most celebrated mods, and transform its core idea into a game of its own. Factorio's Ultracube, which limits production to the vicinity of the eponymous cube and tasks players with expertly navigating the bottlenecks that inevitably brings, is a lauded but daunting twist on the genre leader. By the time Substructure's devs have finished showing me how their game reimagines that idea across a multi-level map, I'm feeling dizzy at the extent of mental juggling I've had to do.

After a 'rogue planet' drifts its way into the solar system, you're dispatched to its surface to investigate. Upon arrival, you quickly begin extracting the resources you find near your landing site; silica serves as a basic building material, from which you can construct what you need to farm the local fauna, burning it as biofuel to power more complex buildings. Automation, of course, is the aim, and conveyors and robotic arms are quickly sorting and transporting fuel, raw materials, and seeds to be replanted around your growing planetary footprint.

Rock and roll

But among the more simple material is something else; a rock that can only be mined at night, and which will eventually dissolve away if not processed effectively. It's the first sense of the logistical challenges that Substructure will impose, but also that there's more to this planet than the plants and minerals on its surface are ready to reveal. Eventually, a drill allows you to burst through the crust, opening a cavernous new internal frontier to explore.

It's from here that the real complexity of Substructure's automation begins to open up. Beneath the outer shell, the planet has another level, this one dark, humid, and home to bioluminescent fungus. Bore down another layer and the climate changes again, glowing crystals combining with a building toxicity to create an altogether harsher climate. Developer Dubious Design has already teased a journey taking you all the way to the planet's core, and the deeper you delve the more clues you'll find to suggest this rogue planet hasn't always been as empty as it currently seems.

But, while progress might be downwards, it's not a straight line. Those drills don't simply allow you to bust holes in the planet for the fun of it – they help you build massive elevator shafts that can be used to carry materials to and fro across the various levels you've explored. Material mined from lower levels might need to be brought up to the surface for expansion, and material processed on the surface will need to go back into the depths.

As your automation becomes more complex, the elevators themselves can become their own mega-factories, yoyo-ing between levels to take advantage of the differing environmental conditions. Certain catalysts will speed up production – sunlight, for example, speeds up the production of the plants in your fields, while darkness will slow it down – so managing exactly where your elevators are and at what thresholds they move (all while balancing where their output goes) is crucial to pushing substructure's efficiency.

By the time just three planetary levels have offered up their secrets, my head is spinning. I'm being guided through Substructure's opening hours at breakneck pace, admittedly, but there are already so many moving parts, all reliant on so many other systems. Despite that, studio co-founders Mike Donoghue and Stu Taylor say they have to fight the urge to add things that are "too complicated."

Instead, the aim is to gradually introduce players to more and more complex ideas. Guiding them directly through the experience isn't an option – the team's internal mantra is "'all game'", the idea that nothing should be interrupting the player on their own journey to understanding. Mastery might be a long time coming, but the belief is that that friction – catalysts, time-sensitive resources, the game's sheer verticality – is all a necessary part of the game.

"You need friction for it to be interesting," says Taylor, as Donoghue doubles down: "I think humans derive inherent satisfaction from solving things and feeling like they've achieved something. We really believe in this idea of 'sense of accomplishment by playing', where indirect guidance is where you get the highest sense of accomplishment. Our games work best to some extent when they are maddening you."

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