A hybrid modal dialog: docked beside these controls when there's room, a modal window when there isn't, and full screen - with a back arrow - on a phone-sized screen.

• Open it, then resize the window: the very same dialog component moves between the three - so its state (the counter) is simply kept, never saved and restored.
• Open, the dialog has a URL of its own (/hybrid-modal-dialog/dialog): link to it, reload it, and the browser's back button closes it - as a phone's back gesture would.