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
diff --git a/2015/day22-input b/2015/day22-input
new file mode 100644
index 0000000..7f98dd7
--- /dev/null
+++ b/2015/day22-input
@@ -0,0 +1,2 @@
+Hit Points: 58
+Damage: 9
diff --git a/2015/day22.py b/2015/day22.py
new file mode 100644
index 0000000..2441242
--- /dev/null
+++ b/2015/day22.py
@@ -0,0 +1,139 @@
+with open('day22-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])
+player_hp = 50
+player_mp = 500
+
+from collections import namedtuple
+State = namedtuple('State', ['player_hp', 'player_mp', 'boss_hp', 'shield', 'poison', 'recharge', 'mp_spent'])
+
+initial_state = State(player_hp, player_mp, boss_hp, 0, 0, 0, 0)
+
+def magic_missile(state):
+  if state.player_mp < 53:
+    raise ValueError('Not enough mana')
+  return State(state.player_hp, state.player_mp-53, state.boss_hp-4,
+               state.shield, state.poison, state.recharge, state.mp_spent+53)
+
+def drain(state):
+  if state.player_mp < 73:
+    raise ValueError('Not enough mana')
+  return State(state.player_hp+2, state.player_mp-73, state.boss_hp-2,
+               state.shield, state.poison, state.recharge, state.mp_spent+73)
+
+def poison(state):
+  if state.player_mp < 173:
+    raise ValueError('Not enough mana')
+  if state.poison > 0:
+    raise ValueError('Already poisoned')
+  return State(state.player_hp, state.player_mp-173, state.boss_hp,
+               state.shield, state.poison+6, state.recharge, state.mp_spent+173)
+
+def shield(state):
+  if state.player_mp < 113:
+    raise ValueError('Not enough mana')
+  if state.shield > 0:
+    raise ValueError('Already shielded')
+  return State(state.player_hp, state.player_mp-113, state.boss_hp,
+               state.shield+6, state.poison, state.recharge, state.mp_spent+113)
+
+def recharge(state):
+  if state.player_mp < 229:
+    raise ValueError('Not enough mana')
+  if state.recharge > 0:
+    raise ValueError('Already recharging')
+  return State(state.player_hp, state.player_mp-229, state.boss_hp,
+               state.shield, state.poison, state.recharge+5, state.mp_spent+229)
+
+def turn_start(state, hardmode_player_turn=False):
+  s = state._asdict()
+  if hardmode_player_turn:
+    s['player_hp'] -= 1
+    if s['player_hp'] <= 0:
+      return State(**s)
+  if s['recharge'] > 0:
+    s['player_mp'] += 101
+    s['recharge'] -= 1
+  if s['poison'] > 0:
+    s['boss_hp'] -= 3
+    s['poison'] -= 1
+  if s['shield'] > 0:
+    s['shield'] -= 1
+  return State(**s)
+
+def boss_action(state):
+  damage = boss_damage
+  if state.shield > 0:
+    damage = max(damage-7, 1)
+  return State(state.player_hp-damage, state.player_mp, state.boss_hp,
+               state.shield, state.poison, state.recharge, state.mp_spent)
+
+spells = [magic_missile, drain, shield, poison, recharge]
+mana_reqs = [53, 73, 113, 173, 229]
+def execute_round(state, command, hardmode=False):
+  state = turn_start(state, hardmode)
+  if state.player_hp <= 0:
+    return state
+  state = spells[command](state)
+  state = turn_start(state)
+  if state.boss_hp > 0:
+    state = boss_action(state)
+  return state
+
+maximum_mana_usage = 100000  # Arbitrarily large
+winning_commands = []
+def tree_simulation(state, commands, hardmode=False):
+  global maximum_mana_usage, winning_commands
+
+  state = execute_round(state, commands[-1], hardmode)
+  if state.player_hp <= 0 or state.mp_spent > maximum_mana_usage:
+    return 100000
+  if state.boss_hp <= 0:
+    maximum_mana_usage = state.mp_spent
+    winning_commands = commands
+    return state.mp_spent
+
+  mp_spent = 100000
+  for cmd, mana in enumerate(mana_reqs):
+    if state.player_mp > mana:
+      try:
+        mp_spent = min(tree_simulation(state, commands+[cmd], hardmode), mp_spent)
+      except ValueError:
+        pass
+  return mp_spent
+
+mana = min([tree_simulation(initial_state, [c]) for c in range(len(spells))])
+print(mana)  # Part 1
+part1_commands = winning_commands
+
+maximum_mana_usage = 100000
+mana_hard = min([tree_simulation(initial_state, [c], hardmode=True) for c in range(len(spells))])
+print(mana_hard)  # Part 2
+part2_commands = winning_commands
+
+# Bonus: show the winning simulations
+spell_names = ['Magic Missile', 'Drain', 'Shield', 'Poison', 'Recharge']
+
+def perform_simulation(command_list, maximum_mana_usage=None, hardmode=False):
+  state = initial_state
+  for i, command in enumerate(command_list):
+    print(state)
+    print(f'Player casts {spell_names[command]}!')
+    try:
+      state = execute_round(state, command, hardmode)
+    except ValueError:
+      return f'Failed at round #{i+1}: Insufficient mana'
+    if maximum_mana_usage and state.mp_spent >= maximum_mana_usage:
+      return f'Failed at round #{i+1}: Exceeded mana budget'
+    if state.player_hp <= 0:
+      return f'Failed at round #{i+1}: Player died'
+    if state.boss_hp <= 0:
+      return f'Succeeded at round #{i+1}', state.mp_spent
+  return f'Ran out of commands but game is not over', state
+
+print('Ideal normal mode fight:')
+print(perform_simulation(part1_commands))
+print('')
+print('Ideal hard mode fight:')
+print(perform_simulation(part2_commands, hardmode=True))