Apple - Support - Discussions - Why has my Mac mini become so slow? ... In a word, it comes down to lag. Every operation which used to be instant when the Mac was new, now has a delay of anything from half a second to over 10 seconds. It feels like walking in mud. And it's always the first time I do something I haven't done for a few minutes -- if I repeat the same operation immediately afterwards, it's instant. Long delays are often (but not always) accompanied by the beachball -- which I see a lot. in Public bookmarkswith applecommentforumfrancoismacminislowsupport
Apple Human Interface Guidelines: Windows An item that provides click-through is one that a user can activate on an inactive window with one click, instead of clicking first to make the window active and then clicking the item. Click-through provides greater efficiency in performing such tasks as closing or resizing inactive windows, and copying or moving files. In many cases, however, click-through could confuse a user who clicks an item unintentionally. in Public bookmarkswith appleclick-throughclickthroughguidelineshumaninterfaceuiwindows