Picnic for SketchStop, Collaborate, and Listen. Picnic is a plugin that allows teammates to work better together in Sketch. It ships with a handy-dandy project viewer so you can see what everyone is working on. First 2 users are free, then $15/user/month. Or, bill annually for $120/user/year.
週刊アスキー - 週アスのITニュースサイト
