diff --git a/2018/ruby/day_13.rb b/2018/ruby/day_13.rb
new file mode 100644
index 0000000..92db0a6
--- /dev/null
+++ b/2018/ruby/day_13.rb
@@ -0,0 +1,122 @@
+Cart = Struct.new(*%i[ x y dir turns ])
+map = ARGF.read.chomp.lines.map(&:chomp).map(&:chars)
+
+carts = []
+map.each.with_index {|row,y|
+  row.each.with_index {|i,x|
+    carts << Cart.new(x, y, i, 0) if %w[ ^ v < > ].include?(i)
+  }
+}
+
+loop do
+  carts.sort_by {|cart|
+    [cart.y, cart.x]
+  }.each do |cart|
+    case cart.dir
+    when ?^
+      cart.y -= 1
+      crashes = carts.select {|candidate| candidate.x == cart.x && candidate.y == cart.y }
+      carts.delete_if {|candidate| crashes.include?(candidate) } if crashes.size > 1
+      case map[cart.y][cart.x]
+      when ?\\
+        cart.dir = ?<
+      when ?/
+        cart.dir = ?>
+      when ?+
+        case cart.turns % 3
+        when 0
+          cart.dir = ?<
+        when 1
+        when 2
+          cart.dir = ?>
+        end
+        cart.turns += 1
+      end
+    when ?v
+      cart.y += 1
+      crashes = carts.select {|candidate| candidate.x == cart.x && candidate.y == cart.y }
+      carts.delete_if {|candidate| crashes.include?(candidate) } if crashes.size > 1
+      case map[cart.y][cart.x]
+      when ?\\
+        cart.dir = ?>
+      when ?/
+        cart.dir = ?<
+      when ?+
+        case cart.turns % 3
+        when 0
+          cart.dir = ?>
+        when 1
+        when 2
+          cart.dir = ?<
+        end
+        cart.turns += 1
+      end
+    when ?<
+      cart.x -= 1
+      crashes = carts.select {|candidate| candidate.x == cart.x && candidate.y == cart.y }
+      carts.delete_if {|candidate| crashes.include?(candidate) } if crashes.size > 1
+      case map[cart.y][cart.x]
+      when ?\\
+        cart.dir = ?^
+      when ?/
+        cart.dir = ?v
+      when ?+
+        case cart.turns % 3
+        when 0
+          cart.dir = ?v
+        when 1
+        when 2
+          cart.dir = ?^
+        end
+        cart.turns += 1
+      end
+    when ?>
+      cart.x += 1
+      crashes = carts.select {|candidate| candidate.x == cart.x && candidate.y == cart.y }
+      carts.delete_if {|candidate| crashes.include?(candidate) } if crashes.size > 1
+      case map[cart.y][cart.x]
+      when ?\\
+        cart.dir = ?v
+      when ?/
+        cart.dir = ?^
+      when ?+
+        case cart.turns % 3
+        when 0
+          cart.dir = ?^
+        when 1
+        when 2
+          cart.dir = ?v
+        end
+        cart.turns += 1
+      end
+    end
+
+    # puts map.map.with_index {|row,y|
+    #   row.map.with_index {|i,x|
+    #     cart = carts.find {|cart| cart.x == x && cart.y == y }
+    #     cart ? cart.dir : i
+    #   }.join
+    # }.join("\n")
+    # puts
+
+    # crashes = Hash.new(0)
+    # carts.each {|cart| crashes[[cart.x, cart.y]] += 1 }
+    # crashes = crashes.select {|_,v| v > 1 }.map(&:first)
+    # crashes.each do |(x,y)|
+    #   p x
+    #   p y
+    #   carts.delete_if {|cart| cart.x == x && cart.y == y }
+    # end
+    if carts.size == 1
+      p carts
+      exit
+    end
+    # if crashes.values.any? {|v| v > 1 }
+    #   p crashes.find {|_,v| v > 1 }
+    #   exit
+    # end
+  end
+
+  # p carts
+  # sleep 1
+end