diff --git a/2025/ruby/Gemfile b/2025/ruby/Gemfile
new file mode 100644
index 0000000..826a354
--- /dev/null
+++ b/2025/ruby/Gemfile
@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+source "https://rubygems.org"
+
+gem "z3"
diff --git a/2025/ruby/Gemfile.lock b/2025/ruby/Gemfile.lock
new file mode 100644
index 0000000..5e00e53
--- /dev/null
+++ b/2025/ruby/Gemfile.lock
@@ -0,0 +1,35 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ffi (1.17.2)
+    ffi (1.17.2-aarch64-linux-gnu)
+    ffi (1.17.2-aarch64-linux-musl)
+    ffi (1.17.2-arm-linux-gnu)
+    ffi (1.17.2-arm-linux-musl)
+    ffi (1.17.2-arm64-darwin)
+    ffi (1.17.2-x86-linux-gnu)
+    ffi (1.17.2-x86-linux-musl)
+    ffi (1.17.2-x86_64-darwin)
+    ffi (1.17.2-x86_64-linux-gnu)
+    ffi (1.17.2-x86_64-linux-musl)
+    z3 (0.0.20251017)
+      ffi (~> 1.17)
+
+PLATFORMS
+  aarch64-linux-gnu
+  aarch64-linux-musl
+  arm-linux-gnu
+  arm-linux-musl
+  arm64-darwin
+  ruby
+  x86-linux-gnu
+  x86-linux-musl
+  x86_64-darwin
+  x86_64-linux-gnu
+  x86_64-linux-musl
+
+DEPENDENCIES
+  z3
+
+BUNDLED WITH
+   2.6.9
diff --git a/2025/ruby/day_10.rb b/2025/ruby/day_10.rb
new file mode 100644
index 0000000..c2af2d8
--- /dev/null
+++ b/2025/ruby/day_10.rb
@@ -0,0 +1,54 @@
+require "z3"
+
+Machine = Data.define(:lights, :schematics, :joltage) do
+  def configure_lights
+    schematics = self.schematics.map { it.inject(0) {|n,i| n + 2**i } }
+    (1..).find {|n|
+      schematics.repeated_combination(n).any? {|presses|
+        presses.inject(0) {|lights, i| lights ^ i } == lights
+      }
+    }
+  end
+
+  def configure_joltage
+    solver = Z3::Optimize.new
+
+    schematics = self.schematics.map.with_index { [_1, Z3.Int("n#{_2}")] }
+
+    solver.minimize(schematics.map(&:last).sum)
+
+    schematics.each do |_, v|
+      solver.assert(v >= 0)
+    end
+
+    joltage.each.with_index do |level, i|
+      solver.assert(
+        schematics.filter_map {|s,v| s.include?(i) && v }.inject(:+) == level
+      )
+    end
+
+    fail unless solver.satisfiable?
+    solver.model.to_h.values.sum(&:to_i)
+  end
+end
+
+machines = DATA.read.lines.map {|line|
+  lights, *schematics, joltage = line.split(/\s+/)
+
+  lights = lights.scan(/[.#]/).map {
+    case it
+    when ?. then 0
+    when ?# then 1
+    else fail
+    end
+  }.join.reverse.to_i(2)
+  schematics = schematics.map { it.scan(/\d+/).map(&:to_i) }
+  joltage = joltage.scan(/\d+/).map(&:to_i)
+
+  Machine.new(lights, schematics, joltage)
+}
+
+pp machines.map(&:configure_lights).sum
+pp machines.map(&:configure_joltage).sum
+
+__END__