Edit List (Mail, Split View)

I really like this interaction on several levels.

Initial click to edit switches button to say cancel (follows Symmetry of interaction I discuss in my talks -- similar to basecamp's group edit)

Slight delay before bringing in contextual edit tools (checkboxes for selecting items to delete).

Select affordances slide in from left as content slides right -- grabs attention.

Selecting messages from the list increments the number of items to delete in the Delete button below as well as bright red checkbox matching the delete button's color.

Unselecting one of the messages causes the stack to fold down and "let" the message back into the list (keeping it full size as it goes back into the list).

As each item is selected the mail message (in the detail pane to the right) shrinks down slightly and the group begins to form a pile. Great animation of the each message flying into the pile. Also note there is a delay between when the item flies into the pile and when it was selected. Seems the delay really stays connected even thought it is much longer than you would do with a mouse. Very interesting.

Hitting DELETE causes the button to grow large in response.

The stack shrinks down and flies down into the general area of the delete button (but not right into it). I personally would have sent it off to the right or made it poof in a puff of smoke but I am sure there was some research around the way it flies toward the list/action. Shrinking the stack indicates it is going away (being deleted).