The initial draft of the Use Cases & Requirements document. Per our 6 February 2018 kickoff, the document should: be fairly short (1.5k-2k words); describe the problem space / need for container queries; avoid a specific syntactic/technical proposal (#22). (Also, the Responsive Images specification has excellent sections for Use Cases & Requirements, which could be a helpful model. Though as noted, they’re longer / more detailed than we’ll need.)