This is a very simple web tool to "discover" maps. The main usecase is pen-and-paper role-playing games, in which you want to show a map but piece by piece, as the characters explore it.
The idea is: the narrator loads a map (say, in a laptop or a tablet) and selects which parts of the map should be shown first. Then, toggles full opacity so that only the uncovered parts show. Now the laptop or tablet can be shown to the players, which will only see the parts the narrator wants. As they explore the map, the narrator can get the tablet, toggle partial opacity, uncover a bit more of the map, toggle full opacity again and show the result to the players.
You can download the code and make modifications, or simply use it online.
- Allow changing the size of pencil?