diff --git a/2021/ruby/day_04.rb b/2021/ruby/day_04.rb
new file mode 100644
index 0000000..2b0a6e0
--- /dev/null
+++ b/2021/ruby/day_04.rb
@@ -0,0 +1,29 @@
+input = ARGF.read
+numbers, *cards = input.split("\n\n")
+numbers = numbers.split(?,).map(&:to_i)
+cards = cards.map {|c| c.split("\n").map {|r| r.split(/\s+/).reject(&:empty?).map(&:to_i) }}
+
+def win?(card, drawn)
+  return true if card.any? {|row| row.all? {|c| drawn.include?(c) }}
+  return true if card.transpose.any? {|col| col.all? {|c| drawn.include?(c) }}
+  # return true if (0..4).all? {|x| drawn.include?(card.fetch(x).fetch(x)) }
+  # return true if (0..4).all? {|x| drawn.include?(card.fetch(x).fetch(4-x)) }
+  return false
+end
+
+(0..numbers.length).each do |i|
+  drawn = numbers[0..i]
+
+  # winning_card = cards.find {|c| win?(c, drawn) }
+  # if winning_card
+  #   p winning_card.flatten.reject {|x| drawn.include?(x) }.sum * drawn.last
+  #   exit
+  # end
+
+  if cards.length == 1 && winning_card = cards.find {|c| win?(c, drawn) }
+    p winning_card.flatten.reject {|x| drawn.include?(x) }.sum * drawn.last
+    exit
+  else
+    cards = cards.reject {|c| win?(c, drawn) }
+  end
+end
diff --git a/2021/ruby/day_05.rb b/2021/ruby/day_05.rb
new file mode 100644
index 0000000..59a64a2
--- /dev/null
+++ b/2021/ruby/day_05.rb
@@ -0,0 +1,29 @@
+vents = ARGF.read.split("\n").map {|l| l.split(" -> ").map {|x| x.split(?,).map(&:to_i) }}
+
+straights = vents.select {|(x1,y1),(x2,y2)| x1 == x2 || y1 == y2 }
+
+points = Hash.new(0)
+straights.each do |(x1,y1),(x2,y2)|
+  x = [x1, x2].minmax
+  y = [y1, y2].minmax
+  (x[0]..x[1]).each do |x|
+    (y[0]..y[1]).each do |y|
+      points[[x,y]] += 1
+    end
+  end
+end
+
+diagonals = vents - straights
+diagonals.each do |(x1,y1),(x2,y2)|
+  if x1 > x2
+    x1,x2 = x2,x1
+    y1,y2 = y2,y1
+  end
+  sign = (y1 < y2) ? 1 : -1
+  (x1..x2).each.with_index do |x,i|
+    delta = i * sign
+    points[[x,y1+delta]] += 1
+  end
+end
+
+p points.count {|_,v| v > 1 }