Press the green flag. Arrow keys to move. Get to the cheese(yellow square) Don't touch black.
One thing that went wrong at first was the first maze I tried to use. I got mazes from the internet, so all the lines in one maze were different shades of black. The new one I found, (https://i.pinimg.com/originals/83/9a/66/839a6666a45e7afca05c3de9afd61f06.jpg), was much more the same color.
