Size and Placement
Design Guidelines
Nesting Dialog Boxes
If a tile or an area is unavailable or irrelevant given the current option settings, disable it immediately so the tile or area is unavailable and the user can't select it. Try not to overuse the disabling tiles feature. Too many unavailable tiles can be distracting.
If a tile displays a value, disabling the tile shouldn't affect the value. The tile should display the same value when it is enabled again. Values that change magically create more work for the user, which is annoying and distracting.