A good concept with a lot of possible room to grow. I'd love to see more types of nodes that do different things, though I had a few minor problems, so here they are in order:
First, assigning the nodes some sprites that explain their behaviur would be nice. I tried to remember them, but it's hard if you only have the color to know them by.
Second, I don't know how familiar you are with your programming enviroment, but to check if a maze is solvable or not shouldn't be too hard to implement. With some extra logic, it could be optimized quite well, but that is rather advanced, so that isn't really a problem, more like a nice feature to have.
Also, the HUD is a bit cramped, so cleaning it up a bit and leaving more space between text would be a good idea I think.