- The whole system of detergent upgrades is basically moot if you just upgrade your basic mop, bucket and sponges. The pressure washer rapidly becomes irrelevant, too.
- The art museum is easily an order of magnitude larger and more complex than everything before it. Be ready to sink a lot of time into it.
- The game shows your completion of tasks only in the area you are in. Take a full tour of the level before leaving if you're going for a perfect score. If going for secrets and collectibles, check a guide.
- There are at least two distinct moments where the game hides the last piece of furniture you need to replace by balancing it on a light fixture above your head & out of your general field of vision. If you find yourself one item short, look up.
- Despite the quest markers telling you that you can leave once all the bodies are picked up & you have no garbage bags lying around, it will not let you leave until you reach 75% completion.
- The ozonator might seem useless but it does exactly what it says it does: it weakens any stains within its pull range, making them easier to mop/sponge up. As your cleaning tools increase in strength this becomes less of an issue, but in larger levels it can be nice to drop the ozonator in a room and let it soften things up while you clean somewhere else.
- Speaking of cleaner vision, it and the flashlight should be your first two upgrades. The benefits of being able to see what you're doing, where you're going and what needs cleaning go without saying. Conversely, the lamp and UV lamp are basically useless; they don't light up a large area, and they're physics objects you now have to clean and maneuver around.