A video demonstration of Upwelling’s main features: viewing drafts with highlighted changes, creating a new draft and sharing it, adding a comment, merging a draft, and comparing document versions in the stack of accepted layers. Upwelling takes a different approach: all drafts float on top of the stack of merged layers; when one draft is merged, all other drafts are updated to include the changes in the merged layer. One way of enforcing “one merge at a time” would be to keep track of the latest stack on a server, and to allow writers to merge onto the stack only if approved by the server (writers would still be able to edit drafts while offline; they would only need to be online to merge a draft).