TODO

major:
	add in game guide
	gui-based system readout:
		absolute count of unfulfilled requests
		item count of unfulfilled requests
		absolute count of available provides (is this even possible without a provide threshold?)
		item count of available provides
		system log
		check out LTN addons that do this for inspiration
	per-station statistics gui
	move to an event based algorithm
	models & art
	dramatically improve the mods handling of invalid entities

minor:
	break the central planner into a separate library
	check if necessary entities can be destroyed without raising events
	improve the behavior of trains if players intervene during deliveries
	handle if signals are removed from the game during migration
	update wagon control combinators immediately upon placement
	close gui when the combinator is destroyed
	do not play close sound when a different gui is opened
	gui can desync if settings are changed outside of it while it is open
	give the combinators a sensible reaction to low or no power
	depot alerts when misconfigured

compat:
	train upgrader mod
	deadlocks signals
	railloader
	picker dollies?
	cargo ships
	editor extensions (test surface separation)
	train fuel types for refuelers
	automatic recipe creation