Examples
Bottom sheet
Click the Open sheet button, then swipe the sheet down to dismiss it: drag it down on a touch screen, scroll up with a mouse wheel, or swipe down with two fingers on a trackpad. The backdrop opacity and the corner radius follow the gesture through the --sheet view timeline, with the --sheet-progress fallback where view timelines are not supported. The close button, the backdrop and Esc close it too. See the required CSS.
Long content
When the content is taller than the screen, the panel scrolls it. Scroll the content down, then drag it back up: once the content reaches its top, the drag chains to the sheet and dismisses it. This story uses the same CSS and JavaScript as the bottom sheet.