My idea for a physics based factory game for mobile? Start with something bouncy and colorable and put them in a swipe friendly tube/well/shaft/whatever:

Then you realize for a theme, those balls could be coins- hey, it could be a mint! Let's engrave them!

But the essence in a factory game not just being a puzzle game is allowing the player to solve logistics on their own, so we need splitters, filters ect.. Here's some filters:

But now that we're in a Mint, we can build more components to polish, grind, and add other effects like rim coloring:

Then you just need to grind out five levels, add some dwarves to help show you the ropes, and you've got a playable demo: Dwarven Mint on Itch