This is a great puzzle game! It reminded me of something i used to play on miniclip as a kid, i cant remember the name
The idea is really fun, where you lay down a safe path behind you, it makes you think about your next move and trying to find the optimal path!
As @JacobSchoen said, there is a bug cutting off the "X coins needed" text when not in fullscreen mode webgl, but that should be pretty easy to fix
Well done and good luck!