FYI, the tech tree doesn't show anything by default - you actually have to select/search a topic.
Addendum:
Nice to see that we finally get an option to put out fires (or burning agents, or aliens...or civilians). Have you thought about adding a one-use option like a
fire blanket? It makes sense to have a fire extinguisher on an aircarft, but lobbing one around while you're being shot at by extraterrestials or monster seems kind of...strange. Fire blankets could be one or two spaces wide, lighter than the extinguisher, but their effect would cover only one square (or 3x3, centered around the target) - they would only be good to actually extinguish fires on units (or very small fires). Something like that would be extremely helpful to keep units that have been set on fire and fall unconscious from dying. I often set units i want to catpure on fire to panic them and soften them up. If they fall unconscious while still on fire they're almost always bound die due to the damage.
BTW, since we already have a large storage facility and large living quarters - any plans to add a large workshop in the future?
