diff --git a/hs/app/Main.hs b/hs/app/Main.hs
index e9f5019..1431398 100644
--- a/hs/app/Main.hs
+++ b/hs/app/Main.hs
@@ -2,10 +2,7 @@ module Main where
 
 import Options.Applicative
 
-import Aoc.Y2019.A01
-import Aoc.Y2019.A02
-import Aoc.Y2019.A03
-import Aoc.Y2019.A04
+import Aoc.Y2019
 
 data Settings = Settings
   { function :: FilePath -> IO ()
@@ -18,6 +15,7 @@ solutions = subparser $ mconcat $ map (\(name, func) -> command name (info (pure
   , ("2019_02", solve201902)
   , ("2019_03", solve201903)
   , ("2019_04", solve201904)
+  , ("2019_05", solve201905)
   ]
 
 parser :: Parser Settings
diff --git a/hs/src/Aoc/Y2019.hs b/hs/src/Aoc/Y2019.hs
new file mode 100644
index 0000000..4f980b4
--- /dev/null
+++ b/hs/src/Aoc/Y2019.hs
@@ -0,0 +1,13 @@
+module Aoc.Y2019
+  ( solve201901
+  , solve201902
+  , solve201903
+  , solve201904
+  , solve201905
+  ) where
+
+import Aoc.Y2019.A01
+import Aoc.Y2019.A02
+import Aoc.Y2019.A03
+import Aoc.Y2019.A04
+import Aoc.Y2019.A05
diff --git a/hs/src/Aoc/Y2019/A05.hs b/hs/src/Aoc/Y2019/A05.hs
new file mode 100644
index 0000000..f530647
--- /dev/null
+++ b/hs/src/Aoc/Y2019/A05.hs
@@ -0,0 +1,117 @@
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+
+module Aoc.Y2019.A05
+  ( solve201905
+  ) where
+
+import           Control.Monad
+import           Data.Bifunctor
+import           Data.Foldable
+import qualified Data.Map.Strict as M
+import           Data.Maybe
+import qualified Data.Set as S
+import qualified Data.Text as T
+import qualified Data.Text.IO as T
+
+-- Basic types
+
+-- Typesafe addresses and values so we don't confuse the two unless we want to.
+
+newtype Addr = Addr Integer
+  deriving (Show, Eq, Ord, Enum, Num, Real, Integral)
+
+newtype Value = Value Integer
+  deriving (Show, Eq, Ord, Enum, Num, Real, Integral)
+
+-- Memory
+
+newtype Memory = Memory { unmemory :: M.Map Addr Value }
+
+instance Show Memory where
+  show mem = "Memory " <> show (memToList mem)
+
+newMem :: [Integer] -> Memory
+newMem = Memory . M.fromList . map (bimap Addr Value) . zip [0..]
+
+memToList :: Memory -> [Integer]
+memToList (Memory m) =
+  let maxAddr = fromMaybe 0 $ S.lookupMax $ M.keysSet m
+  in  map (toInteger . fromMaybe 0 . (m M.!?)) [0..maxAddr]
+
+readMem :: Addr -> Memory -> Maybe Value
+readMem addr (Memory mem) = mem M.!? addr
+
+writeMem :: Addr -> Value -> Memory -> Memory
+writeMem addr val = Memory . M.insert addr val . unmemory
+
+-- State
+
+data State = State
+  { stateMem :: Memory
+  , stateIdx :: Addr
+  , stateInput :: [Integer]
+  } deriving (Show)
+
+newState :: Memory -> State
+newState mem = State mem 0 []
+
+data StepError
+  = Halted
+  | CouldNotRead Addr
+  | UnknownOpcode Integer
+  deriving (Show)
+
+readAt :: State -> Addr -> Either StepError Value
+readAt s i = case readMem i $ stateMem s of
+  Nothing -> Left $ CouldNotRead i
+  Just v -> Right v
+
+writeAt :: Addr -> Value -> State -> State
+writeAt addr val s = s{stateMem = writeMem addr val $ stateMem s}
+
+-- Opcode
+
+data ParamMode = PositionMode | ImmediateMode
+  deriving (Show, Eq)
+
+digits :: Integer -> [Integer]
+digits i = (i `mod` 10) : digits (i `div` 10)
+
+pmFromDigit :: Integer -> ParamMode
+pmFromDigit 0 = PositionMode
+pmFromDigit 1 = ImmediateMode
+pmFromDigit _ = undefined
+
+paramModes :: Integer -> [ParamMode]
+paramModes i = map pmFromDigit $ drop 2 $ (digits i ++ repeat 0)
+
+data Operand = Direct Value | Indirect Addr
+  deriving (Show)
+
+data Opcode
+  = OpAdd Operand Operand Addr
+  | OpMul Operand Operand Addr
+  | OpInput Addr
+  | OpOutput Operand Addr
+  | OpHalt
+  deriving (Show)
+
+opWidth :: Opcode -> Addr
+opWidth (OpAdd    _ _ _) = 4
+opWidth (OpMul    _ _ _) = 4
+opWidth (OpInput  _)     = 2
+opWidth (OpOutput _ _)   = 3
+opWidth  OpHalt          = 1
+
+parseOpcode :: State -> Either StepError Opcode
+parseOpcode s = do
+  let idx = stateIdx s
+  undefined
+
+solve201905 :: FilePath -> IO ()
+solve201905 f = do
+  stuff <- readFile f
+
+  putStrLn ">> Part 1"
+
+  putStrLn ">> Part 2"