Bumping into humans raises the clean levels to max. Seems like you always start with 2 right next to you so it is easy to finish it.
In the dream, i was able to fall off of the platform (i thought it was just a different colored floor) and the stage never finished. Restarted and it seems like you need to die to leave it (maybe add a time or human count limit instead)
The ui could change on gameplay, no need for health in cleaning mode, no need for charge or cleaning in attack mode. Maybe it could be condensed, health and charge be the same bar, and cleaning and a new "bullet amount" the other bar