Thermal Budget an AI datacenter puzzle

You run the floor of a small datacenter. AI labs ship you racks with a deadline attached, and you decide where each rack, power unit and cooling unit goes. Then you press Run and watch the heat spread across the floor.

How do you play?

A rack breathes in through its glowing front and blows hot air out of its back. Point two rows back to back and their heat collects in one hot aisle; face them front to front and they share a cold one. Air handlers push cold air a few tiles down whichever aisle they face, and they pull in whatever is behind them, so one with its back to a hot aisle gets more done. Every rack needs a power unit within two tiles, and the power units only carry so much.

When a rack's intake air goes above 27 °C it slows down, and a slow rack can blow a client's deadline. Past 45 °C it trips and does nothing until it cools off. The heat map (the thermometer button) shows the air temperature on every tile, so you can watch a hotspot form before it costs you.

Each site is scored three ways. You deliver every contract or you lose the site. Then there's a star for spending at or under the target, and one for PUE, power usage effectiveness: the building's total power divided by what the computers use. A PUE of 1.0 would mean the cooling and lights cost nothing.

Where do the numbers come from?

The sites and the clients are made up, and the physics is simplified so a round lasts about a minute. The scale comes from real sources, checked in September 2026:

Racks went from about 8 kW to over 100

Uptime Institute's 2024 global survey put the average rack at about 8 kW. SemiAnalysis reported that an NVIDIA GB200 NVL72 rack, 72 GPUs in one cabinet, needs roughly 120 kW, and it's built for liquid cooling. In the game a GPU rack draws 40 kW and a liquid rack 120.

The average PUE has been stuck near 1.56

That's the figure from the same Uptime survey. Google reports a fleet-wide 1.09 for 2024, which gives you a sense of how far the best sites are from the middle.

Cold intake air

ASHRAE, the engineering society that publishes datacenter thermal guidelines, recommends 18 to 27 °C at a server's intake. That's where the game starts throttling.

Free cooling in the north

Meta's datacenter in Luleå, Sweden is cooled with outside air and runs on power from nearby hydro plants. The fjord level borrows the idea.