The surface is dying. Below it, a few lit rooms can become a home—or a colony that cannot support the people inside.

The Undercity: Last Light is a single-player underground colony simulation. Excavate a city in side-view pixel art, organize its workers, and balance the needs of a growing population against the cost of reaching deeper. Food, water, power and research keep the settlement moving. The people who depend on them give every decision its weight.

Build a colony that works

Dig through the rock and connect rooms with elevators. Turn raw materials into workshops, farms, laboratories, housing and public services. Expand storage, upgrade production and organize shifts to keep supplies flowing. A new room needs more than construction materials: it needs workers, access and a colony able to support it.

Give your people a future

Residents work, form households, grow old and pass on their expertise. Housing shortages, injuries, exhaustion and social tensions affect the colony they live in. Invest in care, education and living conditions—or ask more of a workforce already under pressure.

Choose what the colony can afford

Answer requests, settle disputes and make policy decisions with competing costs. Spend scarce reserves to protect people now, or commit them to the infrastructure you need next. Decisions can change production, morale and future events; their consequences become part of your colony’s record.

Prepare for what the deep brings

Breakdowns and earthquakes test your preparations. Maintain rooms, fund repairs and build safety measures before a warning becomes a crisis. Pause to assess the situation, set priorities, then watch your plans play out.

Discover the world beneath your home

Reach the Thermal Rift, Fungal Sea and Resonant Archive. Each region has its own story, machinery and operating challenges, from heat and water to spores and unstable signals. Bring their systems online and decide how their discoveries should serve your colony.

From refuge to civilization

Undertake multi-stage Grand Projects and choose a Civilization Project that gives your settlement a lasting purpose. Your colony’s story continues beyond that milestone, with the same people, infrastructure and decisions you brought this far.

What will you build below—and what will it cost the people who live there?