Update readme doc

README.md

@@ -1,4 +1,20 @@
 MazeMaker
 =========
 
-TODO
+MazeMaker generates a random block maze and draws the maze in a PNG image.
+The maze is generated by creating a graph, with the array of blocks as
+nodes, and with edges between blocks that are adjacent either up, down,
+left, or right. Random weights are assigned to the edges, and Prim's
+algorithm finds the minimum spanning tree.
+
+The result is a block maze where there are no cycles, every block in the array
+is accessible, and there is exactly one path from any one block to any other.
+The maze is drawn with openings at the lower left and upper right corner,
+suggesting a starting point and ending point.
+
+Usage
+-----
+
+```
+mazemaker -w NUM_BLOCKS -h NUM_BLOCKS output.png
+```