Updated README

README.md

-# Simple procedural generation of "dungeon maps"
+#Simple procedural generation of "dungeon maps"
 
 Basic proof of concept for a "cellular automata" model. No real refinement at this point.
 
-Initial work based on [this tutorial](https://gamedevelopment.tutsplus.com/tutorials/generate-random-cave-levels-using-cellular-automata--gamedev-9664).
+Initial work based on [this tutorial](https://gamedevelopment.tutsplus.com/tutorials/generate-random-cave-levels-using-cellular-automata--gamedev-9664).
+
+It takes the following flags:
+
+* --width *x*: the width of the map. *x* must be a positive integer. See below.
+* --height *x*: the height of the map. *x* must be a positive integer. See below. 
+* --seed *x*: the chance a given cell will be generated as "wall". *x* must be an integer from 1-99.
+* --death *x*: if a wall cell has fewer than this many wall cells surrounding it, it becomes empty. *x* must be an integer from 1-8.
+* --birth *x*: if an empty cell has more than this many wall cells surrounding it, it becomes a wall. *x* must be an integer from 1-8.
+* --reps *x*: the number of smoothing passes to take on the map. *x* must be a positive integer. Large values can significantly extend runtime.
+* --out: save the result to an image in the maps/ directory instead of printing it to the screen.
+
+###A note on width and height
+
+If you use --out, width and height are in pixels.
+
+If you don't, height is lines of text, and width is measured in **chunks of two characters**; "--width 40" will produce a map 80 characters wide. This is because each "wall" cell is represented by a double **I** character and each "empty" cell is represented by a double space; in the font the developer uses, this makes maps where width and height are the same roughly square.