The detail that jumped out at me first is how much information the maker squeezes onto one small screen: CO2, VOC, temperature, humidity and pressure, all displayed on a 1.69 inch display. Five readings on a panel that size is a compact bit of design, and the numbers shown on it looked like live, plausible values rather than a demo loop.
As for how it comes together, the heart of the unit is an ESP32-C6, and the whole thing sits in a 3D-printable case. There is support for an optional LiPo as a power source, which leaves the power arrangement flexible for whoever builds one. Readings go out over Zigbee to Home Assistant, so the monitor slots into a wider setup rather than living only on its own screen.
What stands out most to me is how completely the project is shared: the maker released STLs, the firmware, a parts list and an assembly video, and the firmware is open source. In use, the device was mounted on a 3D printer enclosure, which is exactly where a monitor like this earns its keep.
One thing that was in flux was the licensing. The maker first said the license would be sorted out later, then went ahead and added one after people suggested APACHE2 or GPL3. Anyone planning to reuse the code should check which license ended up being chosen before building on it.