Smooth boosted fleet travel

core/GameState.gd

@@ -2634,12 +2634,24 @@ func _advance_resource_converters(delta: float) -> void:
 		building.conversion_progress = progress
 
 
-func _advance_distorder_drain(delta: float) -> void:
+func _distorder_boost_in_use() -> bool:
+	for fleet in get_tree().get_nodes_in_group("player_fleet"):
+		if fleet.has_method("is_using_speed_boost") and fleet.is_using_speed_boost():
+			return true
+	return false
+
+
+func _advance_distorder_drain(delta: float, boost_in_use: bool = true) -> void:
 	if fleet_speed_multiplier <= 1.0:
 		# Nothing owed at 1.0x - and no stale fractional progress should
 		# carry over into a LATER, unrelated boost.
 		_distorder_drain_progress = 0.0
 		return
+	if not boost_in_use:
+		# The fader is a selected cruise speed, not an always-running machine.
+		# Keep any already-earned fraction so stopping cannot erase a nearly
+		# complete unit of cost, but accrue nothing while the fleet is parked.
+		return
 	# Normalized against the CURRENT ceiling, so "full boost" always costs
 	# ENERGY_DRAIN_PER_SECOND however many distorder vessels widened it -
 	# a bigger fleet buys more speed, not cheaper speed.
@@ -2897,7 +2909,7 @@ func _process(delta: float) -> void:
 	_advance_planning()
 	_advance_repairs(delta)
 	_advance_resource_converters(delta)
-	_advance_distorder_drain(delta)
+	_advance_distorder_drain(delta, _distorder_boost_in_use())
 	_advance_quests()
 	for e in extractors:
 		e.mining_progress = float(e.get("mining_progress", 0.0)) + delta * EXTRACTOR_RATE