This concept is one we have had for awhile: a dedicated software capable of doing any and all prototyping necessary for a board game.
Even in smaller projects we have worked on, we have wanted some software capable of fully prototyping and playtesting our games.
Enter the Board Game Engine, a project created out of need, and a tool we fully intend to use ourselves. This software will, in time, be capable of prototyping nearly any tabletop game you can imagine. We will be hosting it on Steam, with full Workshop integration, for the best experience to not only game designers, but also playtesters.
As for the cost of this application, we only intend to charge for the editor itself. What this means is that the ability to play games will be entirely free, so playtesters will never have to pay simply to participate. The creation of games, pieces, cards, decks, etc. and uploading those items to the Workshop will be part of the paid editor.
We will be releasing on Steam in Early Access initially, because the most intuitive features will come from having the most input from the greatest variety of people. In addition, for essentially helping during our development process, during early access the Board Game Engine will be priced much lower than its final cost. It will reach the final price gradually during early access, and will be at its maximum once out of early access. The project will leave the early access period once all features on our early access list are complete, or we have added additional features to compensate for any that we might not have gotten to.