Countdown is the aspect in every part of the game.
I initially thought the overall time (where the delta subtracts is rather generous)
Then i realized that the max time you can take is from the overall time, and I only had 2.5 seconds at the last level.
All this does not even touch how good this game feels and the smoothness of enemies and the nice mix of the combinations of different enemies and so on.
Really so good!