This should provide a visual clue as to WHERE players
should put tinder to get it to catch properly, since this
seems to be a common problem players run into.
- Expanded fire api, added "check" varieties of things that also
perform relevant checks for eligibility. Standardized testing
for ventilation.
- Snuff embers to coals as fuel.
- Fuel is consumed randomly by flames. This means that fuel that
are surrounded by flame burn out quicker, while flames
surrounded by fuel consume fuel from each node slower. This
adds subtlety to furnace design for efficiency.
