MyGameMill.com is a web platform which allows game designers (board, card, and other tabletop games) to design and playtest their games all online.
Games are created by uploading assets (board images, dice images, card images, rules, etc...) to create game components. Players will be able to choose from a library of pre-existing components, as well. Components are then assigned mechanics like random dice rolls or card shuffling. Once the components are set a beginning game state is created which is saved for future playtests.