diff --git a/2023/ruby/day_10.rb b/2023/ruby/day_10.rb
index ec848d8..09918ca 100644
--- a/2023/ruby/day_10.rb
+++ b/2023/ruby/day_10.rb
@@ -84,6 +84,7 @@ p y_range.sum {|y|
     a = loop_.fetch([y, x_a], nil)
     b = loop_.fetch([y, x_b], nil)
 
+    # it's a chunk if it's multiple empty tiles or a pipe that goes east
     (a.nil? && b.nil?) || (a && TILE_NEIGHBOR_DELTAS.fetch(a).include?([0,1]))
   }.select {|chunk|
     # keep empty tiles