if my os was a workbench:
* i could only have one tool visibible at once.
* one tool must be the main tool.
* thing i was using the tools on, the "subject", is only visibile when using the main tool
* whenever i reached for another tool - the subject had to be hidden and scrambled into the big pile of tools i have
* if had more subjects / projects - whenever i stoped working on it i would either
	- pack it and all tools used for it away in a box and put it on top shelf or
	- put it into the pile of tools and subjects