The "Completed" wasn't always shown or only halfway, its position should be adjusted to what part of the map is currently visible.
As for additions I would think some UI showing how many enemies of which type have been hit would be nice, even if there's no scoring. Or maybe if you wanted to give the player a hint of how many more to get without spoiling too much, you could assign different scores to them and give a level goal to reach (so, is 400 more points one big tough guy or a hole swarm of smaller ones?).
And maybe some sort of mini map. Nothing detailed with too many spoilers, but a rectangle and a blip on the current position to give an idea of which direction(s) to explore next would be nice...