diff --git a/2016/ruby/day_25.rb b/2016/ruby/day_25.rb
new file mode 100644
index 0000000..491b903
--- /dev/null
+++ b/2016/ruby/day_25.rb
@@ -0,0 +1,43 @@
+class Assembunny
+  attr_reader :data
+
+  def initialize(data)
+    @data = data
+  end
+
+  def run(input)
+    return enum_for(__method__, input) unless block_given?
+
+    registers = { ?a => input, ?b => 0, ?c => 0, ?d => 0 }
+    pc = 0
+
+    while pc < data.size
+      line = data[pc]
+      case line
+      when /cpy ([a-d]|\d+) ([a-d])/
+        value = registers.fetch($1) { $1.to_i }
+        registers[$2] = value
+        pc += 1
+      when /inc ([a-d])/
+        registers[$1] += 1
+        pc += 1
+      when /dec ([a-d])/
+        registers[$1] -= 1
+        pc += 1
+      when /jnz ([a-d]|\d+) (-?\d+)/
+        value = registers.fetch($1) { $1.to_i }
+        pc += value.zero? ? 1 : $2.to_i
+      when /out ([a-d])/
+        yield registers.fetch($1)
+        pc += 1
+      else
+        raise "invalid line: #{line}"
+      end
+    end
+  end
+end
+
+assembunny = Assembunny.new(ARGF.read.split("\n"))
+
+needle = ('01' * 6).chars.map(&:to_i)
+puts (1..Float::INFINITY).find {|i| assembunny.run(i).take(12) == needle }