diff --git a/Estinen.cabal b/Estinen.cabal
index 2de1f84..eb6075b 100644
--- a/Estinen.cabal
+++ b/Estinen.cabal
@@ -68,6 +68,9 @@ library
 
     -- Other library packages from which modules are imported.
     build-depends:    base >=4.19.2.0
+                    , matrix
+                    , vector
+                    , parallel
 
     -- Directories containing source files.
     hs-source-dirs:   src
diff --git a/README.md b/README.md
index da1b723..8567ba5 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,30 @@
 # Estinen
 
-Sudo solver written in haskell
\ No newline at end of file
+Sudoku solver written in haskell
+
+
+## Format for input files
+
+```
+1 2 3 4 5 6 7 8 9
+2 3 4 5 6 7 8 9 1
+3 4 5 6 7 8 9 1 2
+4 5 6 7 8 9 1 2 3
+5 6 7 8 9 1 2 3 4 
+6 7 8 9 1 2 3 4 5 
+7 8 9 1 2 3 4 5 6 
+8 9 1 2 3 4 5 6 7 
+9 1 2 3 4 5 6 7 8 
+```
+
+```
+1 2 3 4 5 6 X 8 9
+2 X 4 5 6 X 8 X 1
+3 4 5 X 7 8 9 1 2
+4 5 6 7 8 X 1 2 3
+5 X X 8 9 1 2 3 4 
+6 7 8 9 X 2 3 X X 
+7 X 9 1 2 3 X X X 
+8 9 1 X 3 4 5 6 X 
+9 1 2 3 4 5 6 7 8 
+```
diff --git a/app/Main.hs b/app/Main.hs
index 76e4cc6..c28d901 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,5 +1,11 @@
+{-# LANGUAGE LambdaCase #-}
 module Main where
 
+import Sudoku
+import System.Environment (getArgs)
+
+
 main :: IO ()
-main = do
-  putStrLn "Hello, Haskell!"
+main = getArgs >>= \case
+  [filename] -> readFile filename >>= print . parseStringToGrid
+  _ -> error "Usage: Estinen filename"
diff --git a/invalid.sudoku b/invalid.sudoku
new file mode 100644
index 0000000..578628e
--- /dev/null
+++ b/invalid.sudoku
@@ -0,0 +1,9 @@
+1 2 3 4 5 6 X 9 9
+2 X 4 5 6 X 8 X 1
+3 4 5 X 7 8 9 1 2
+4 5 6 7 8 X 1 2 3
+5 X X 8 9 1 2 3 4
+6 7 8 9 X 2 3 X X
+7 X 9 1 2 3 X X X
+8 9 1 X 3 4 5 6 X
+9 1 2 3 4 5 6 7 8
diff --git a/src/Sudoku.hs b/src/Sudoku.hs
index 6cfc70e..dffd151 100644
--- a/src/Sudoku.hs
+++ b/src/Sudoku.hs
@@ -1 +1,131 @@
-module Sudoku where
+{-# LANGUAGE OverloadedStrings, LambdaCase, MultiWayIf #-}
+module Sudoku ( isValid
+              , Cell(..)
+              , Grid(..)
+              , updateCell
+              , emptyGrid
+              , parseStringToGrid
+              ) where
+
+import Data.Matrix hiding (getRow, getCol)
+import Data.Matrix qualified as M
+import Data.Vector (Vector)
+import Data.Vector qualified as V
+import Data.Coerce
+import Control.Parallel
+import Control.Parallel.Strategies
+
+data Cell where
+  One :: Cell
+  Two :: Cell
+  Three :: Cell
+  Four :: Cell
+  Five :: Cell
+  Six :: Cell
+  Seven :: Cell
+  Eight :: Cell
+  Nine :: Cell
+  Unknown :: Cell
+  deriving (Eq)
+
+instance Show Cell where
+  show One = "1"
+  show Two = "2"
+  show Three = "3"
+  show Four = "4"
+  show Five = "5"
+  show Six = "6"
+  show Seven = "7"
+  show Eight = "8"
+  show Nine = "9"
+  show Unknown = " "
+
+cellFromChar :: String -> Cell
+cellFromChar "1" = One
+cellFromChar "2" = Two
+cellFromChar "3" = Three
+cellFromChar "4" = Four
+cellFromChar "5" = Five
+cellFromChar "6" = Six
+cellFromChar "7" = Seven
+cellFromChar "8" = Eight
+cellFromChar "9" = Nine
+cellFromChar "X" = Unknown
+cellFromChar  _  = error "Unknown char"
+
+numbers :: Vector Cell
+numbers = V.fromList [One, Two, Three, Four, Five, Six, Seven, Eight, Nine]
+
+newtype Column = Column (Vector Cell)
+newtype Row = Row (Vector Cell)
+-- Square is 3x3 
+newtype Square = Square (Matrix Cell)
+-- Grid is 9x9
+newtype Grid = Grid (Matrix Cell)
+
+instance Show Grid where
+  show (Grid m) = prettyMatrix m
+
+parseStringToGrid :: String -> Grid
+parseStringToGrid str =
+  let m = M.fromLists . fmap (fmap cellFromChar) . fmap words . lines $ str
+      rows = nrows m
+      cols = nrows m
+  in if
+    | rows == 9 && cols == 9 && isValid (Grid m) -> Grid m
+    | rows == 9 && cols == 9 -> error "Grid was not valid"
+    | otherwise -> error "String did not fit a sudoku grid"
+
+isValidVector :: Vector Cell -> Bool
+isValidVector = V.all (<= 1) . (numbers >>=) . (((pure . V.length) .) . (. (==)) . flip V.filter)
+
+isValidColumn :: Column -> Bool
+isValidColumn = isValidVector . coerce
+
+isValidRow :: Row -> Bool
+isValidRow = isValidVector . coerce
+
+isValidSquare :: Square -> Bool
+isValidSquare = isValidVector . getMatrixAsVector . coerce
+
+getRow :: Int -> Grid -> Row
+getRow n
+  | n > 0 && n <= 9 = Row . M.getRow n . coerce
+  | otherwise       = error "Indexing row outside of grid"
+
+getColumn :: Int -> Grid -> Column
+getColumn n
+  | n > 0 && n <= 9 = Column . M.getCol n . coerce
+  | otherwise       = error "Indexing column outside of grid"
+
+getSquare :: Int -> Grid -> Square
+getSquare n
+  | n > 0 && n <= 9 = let !sr = (n+2) `div` 3
+                          !er = sr + 2
+                          !sc = (n+2) `mod` 3 + 1
+                          !ec = sc + 2
+                      in Square . submatrix sr er sc ec . coerce
+  | otherwise       = error "Indexing square outside of grid"
+
+isValid :: Grid -> Bool
+isValid g = and $ flip (parMap rpar) [1..9]
+                   (\i ->
+                      let row = isValidRow (getRow i g)
+                          col = isValidColumn (getColumn i g)
+                          square = isValidSquare (getSquare i g)
+                      in col `par` square `par` row && col && square
+                   )
+
+updateCell :: Int -> Int -> Cell -> Grid -> Grid
+updateCell n m 
+  | n > 0 && n <= 9 && m > 0 && m <= 9 = \ c g ->
+      let mx = coerce g in
+      if (mx M.! (n,m) == Unknown) then
+        coerce $ setElem c (n,m) mx else
+        error "Updating non unkown value"
+  | otherwise = error "Updating cell outside of grid"
+  
+emptyGrid :: Grid
+emptyGrid = coerce $ matrix 9 9 (const Unknown)
+
+
diff --git a/valid.sudoku b/valid.sudoku
new file mode 100644
index 0000000..db932bd
--- /dev/null
+++ b/valid.sudoku
@@ -0,0 +1,9 @@
+1 2 3 4 5 6 X 8 9
+2 X 4 5 6 X 8 X 1
+3 4 5 X 7 8 9 1 2
+4 5 6 7 8 X 1 2 3
+5 X X 8 9 1 2 3 4
+6 7 8 9 X 2 3 X X
+7 X 9 1 2 3 X X X
+8 9 1 X 3 4 5 6 X
+9 1 2 3 4 5 6 7 8