diff --git a/2022/ruby/day_23.rb b/2022/ruby/day_23.rb
new file mode 100644
index 0000000..6278326
--- /dev/null
+++ b/2022/ruby/day_23.rb
@@ -0,0 +1,50 @@
+grove = {}
+ARGF.read.lines(chomp: true).each.with_index do |row, y|
+  row.chars.each.with_index do |c, x|
+    grove[[y,x]] = c == ?#
+  end
+end
+
+dirs = [
+  [[-1, -1], [-1,  0], [-1,  1]],
+  [[ 1, -1], [ 1,  0], [ 1,  1]],
+  [[-1, -1], [ 0, -1], [ 1, -1]],
+  [[-1,  1], [ 0,  1], [ 1,  1]],
+]
+
+(1..).each do |i|
+  proposals = grove.select { _2 }
+    .to_h {|(y,x),_|
+      to = if dirs.flatten(1).none? {|dy,dx| grove[[y+dy, x+dx]] }
+             [y, x]
+           elsif dir = dirs.find {|adj| adj.none? {|dy,dx| grove[[y+dy, x+dx]] }}
+             dy, dx = dir[1]
+             [y+dy, x+dx]
+           else
+             [y, x]
+           end
+      [[y,x], to]
+    }
+
+  proposals.each.with_object(Hash.new {|h,k| h[k] = []}) {|(from, to), conflicts|
+    conflicts[to] << from
+  }.select { _2.size > 1 }.values.flatten(1).each do |elf|
+    proposals[elf] = elf
+  end
+
+  if proposals.all? { _1 == _2 }
+    puts i
+    exit
+  end
+
+  proposals.each do |from, to|
+    grove[from] = false
+    grove[to] = true
+  end
+
+  dirs.push(dirs.shift)
+end
+
+# y = grove.select { _2 }.keys.map(&:first).minmax
+# x = grove.select { _2 }.keys.map(&:last).minmax
+# p Range.new(*y).sum {|y| Range.new(*x).count {|x| !grove[[y,x]] }}