Simple WemosD1 mini based CO2 air quality sensor looking like cloud.
It has attached Air Quality - CCS811 TVOC/eCO2 Sensor , and WS2812b led strip for signalizing actual status.
It is sending data through MQTT to HASS server.
You can download firmware and see more details of build at github page of Air quality sensor.
I just clipped wemos inside and glued RGB strip, everything holds together with few drops of superglue.
I found out that problem with stability is caused by high temperature from LED strip and ESP itself, so I uploaded v2 version with more ventilation holes and inner walls in hope for better performance. Currently I am testing this design, if it won't help I will probably add some fan to force movement of air inside.