The site just presents a chess board covered in "rocks" (obstacles) and a goal square you need to get to. It tells you the minimum number of moves it can be done in, and will show you a best solution if you don't get there in it. You can use the settings to change difficulty etc.
A friend then pointed me to https://lichess.org/learn which is also really nice ;) But, it was fun putting it together. Anyway, maybe some of you with young-ones will find it a fun diversion for them :)
Vue and CM-Chessboard[1] for the board rendering, very nice library that one.