diff --git a/main.scm b/main.scm
index 353ef105ea64b779c4bc9b1ebae1135fce182fa8..3e6c1e3b01973bc68ca99d84d250f9b370003b87 100755
--- a/main.scm
+++ b/main.scm
@@ -132,6 +132,9 @@
           (decimals x))
        1))
 
+;; distance from x wall, horizontal wall, wall paralell with the x axis
+;; returns how far you would have to travel in direction a before you
+;; hit a wall.
 (define (y-from-edge y a)
   "distance-from-x-wall"
   (mod (* (sgn (sin a))