Great demo. Core mechanic of sucking up sludge and seeing the area get cleaner is solid. I particularly liked the strategy involved in cleaning specific items/areas to gain the bonus coins in a level I couldn't 100% clean. Art is fantastic, and I'm eager/hopeful to see more locales to clean up.
A couple of criticisms:
1. Lack of variety in upgrades. Hopefully the full game has a bit more choice in terms of how to spend my money other than "longer, better sucking."
2. Balancing - the most time-efficient way to earn income in this demo is actually just to clean the first level over and over again. It was a bit sad to spend longer attempting to clean a new map and being rewarded with less money for my trouble, even when I tried to go for the bonuses as much as possible.
3. The processing minigame needs some work. There's not much advantage to speeding up the actual processing time, because it'll be done by the time you've finished a map, and having to press and wait several times to get it started is just pretty annoying. Have you considered instead a system where, for example, you limit the amount of raw resources you can process each cycle and offer upgrades to increase that capacity, or the conversion rate? That way you would incentivise the player to strategically upgrade their processing capabilities to balance their resources (money/processed currency).