diff --git a/2015/day21-input b/2015/day21-input
new file mode 100644
index 0000000..c5f2409
--- /dev/null
+++ b/2015/day21-input
@@ -0,0 +1,3 @@
+Hit Points: 109
+Damage: 8
+Armor: 2
diff --git a/2015/day21.py b/2015/day21.py
new file mode 100644
index 0000000..c117d56
--- /dev/null
+++ b/2015/day21.py
@@ -0,0 +1,69 @@
+with open('day21-input', 'r') as file:
+  data = [l.strip('\n') for l in file]
+boss_hp = int(data[0].split()[-1])
+boss_damage = int(data[1].split()[-1])
+boss_armor = int(data[2].split()[-1])
+
+player_hp = 100
+player_damage = 0
+player_armor = 0
+
+def attack_damage(damage, armor):
+  return max(damage - armor, 1)
+
+from math import ceil
+def time_to_kill(damage, armor, hp):
+  return ceil(hp/attack_damage(damage, armor))
+
+s_shop_w = """
+Weapons:    Cost  Damage  Armor
+Dagger        8     4       0
+Shortsword   10     5       0
+Warhammer    25     6       0
+Longsword    40     7       0
+Greataxe     74     8       0
+""".split('\n')[2:-1]
+
+s_shop_a = """
+Armor:      Cost  Damage  Armor
+Leather      13     0       1
+Chainmail    31     0       2
+Splintmail   53     0       3
+Bandedmail   75     0       4
+Platemail   102     0       5
+""".split('\n')[2:-1]
+
+s_shop_r = """
+Rings:      Cost  Damage  Armor
+Damage +1    25     1       0
+Damage +2    50     2       0
+Damage +3   100     3       0
+Defense +1   20     0       1
+Defense +2   40     0       2
+Defense +3   80     0       3
+""".split('\n')[2:-1]
+
+weapons = [[int(i) for i in w.split()[-3:]] for w in s_shop_w]
+armors = [[int(i) for i in a.split()[-3:]] for a in s_shop_a] + [[0,0,0]]
+rings = [[int(i) for i in r.split()[-3:]] for r in s_shop_r] + [[0,0,0], [0,0,0]]
+
+def strategy_works(items):
+  # cost = sum([i[0] for i in items])
+  damage = sum([i[1] for i in items])
+  armor = sum([i[2] for i in items])
+  return time_to_kill(damage, boss_armor, boss_hp) <= time_to_kill(boss_damage, armor, player_hp)
+
+from itertools import combinations
+good_strategies = []
+bad_strategies = []
+for w in weapons:
+  for a in armors:
+    for r1, r2 in combinations(rings, 2):
+      strat = (w, a, r1, r2)
+      if strategy_works(strat):
+        good_strategies.append(strat)
+      else:
+        bad_strategies.append(strat)
+
+print(min([sum([i[0] for i in items]) for items in good_strategies]))  # Part 1
+print(max([sum([i[0] for i in items]) for items in bad_strategies]))  # Part 2