Dijkstra's Algorithm Maze Solver

I made this illustration of Dijkstra's Algorithm in high school, but it's still one of the coolest things I've ever made visually. You can check out the source code here, just keep in mind this was high school, so the code is not pretty and very inefficient.

The underlying graph is a simple grid, where nodes are connected vertically and horizontally with unit distance. When you draw a wall, I set the node be initially visited, which avoids drawing a shortest path through the wall when running the algorithm.