- Grey when incompatible simultaneous connections
- Multiple layers of cogs, or perhaps belts to connect cogs?
- Cogs with different colors / styles
- How to check if the teeth of two cogs can fit in each other?
Perhaps: Outer distance between the teeth of cog 1 should be greater
than outer width of the teeth of cog 2, and vice versa.
- Drag'n'drop instead of click'n'move?