diff --git a/2021/day14.hs b/2021/day14.hs
new file mode 100644
index 0000000..0675ff5
--- /dev/null
+++ b/2021/day14.hs
@@ -0,0 +1,43 @@
+{-# LANGUAGE TupleSections #-}
+module Day14 where
+
+import qualified Data.Map as M
+import Data.List (sort, sortOn)
+
+type Pair = (Char,Char)
+type PairInsertion = M.Map Pair Char
+
+parseRule :: String -> (Pair,Char)
+parseRule (a:b:s) = ((a,b), last s)
+
+convertPair :: PairInsertion -> Pair -> [Pair]
+convertPair m p@(a,b) = case M.lookup p m of
+    Just c -> [(a,c), (c,b)]
+    Nothing -> [(a,b)]
+
+stepPairs :: PairInsertion -> [(Pair,Int)] -> [(Pair, Int)]
+stepPairs m = M.assocs . M.fromListWith (+) . concatMap (\(p,i) -> map (\np -> (np,i)) (convertPair m p))
+
+pairsToCount :: [(Pair, Int)] -> [(Char, Int)]
+pairsToCount = map (\(c,i) -> (c, (i+1)`div`2)) . M.assocs . M.fromListWith (+) . concatMap (\((a,b), freq) -> [(a,freq), (b,freq)])
+
+stringToPairs :: String -> [Pair]
+stringToPairs s = zip s (tail s)
+
+main :: IO ()
+main = do
+    template <- map (\p -> (p,1)) . stringToPairs <$> getLine
+    getLine
+    transforms <- M.fromList . map parseRule . lines <$> getContents
+    print $ pairsToCount template
+
+    putStr "part 1: "
+    let step10 = sortOn snd $ pairsToCount $ iterate (stepPairs transforms) template !! 10
+    print $ snd (last step10) - snd (head step10)
+
+    putStr "part 2: "
+    let step10 = sortOn snd $ pairsToCount $ iterate (stepPairs transforms) template !! 40
+    print $ snd (last step10) - snd (head step10)
+
+
+    print "Bye"
diff --git a/2021/day15.hs b/2021/day15.hs
new file mode 100644
index 0000000..a0abb37
--- /dev/null
+++ b/2021/day15.hs
@@ -0,0 +1,65 @@
+module Day15 where
+import Data.Array
+import Data.Char (digitToInt)
+import Debug.Trace (trace, traceShow)
+import Data.Maybe (fromJust, mapMaybe)
+import Data.List (nub, sort)
+
+type Cavern = [[Int]]
+
+neighs :: Int -> Int -> Int -> Int -> [(Int,Int)]
+neighs max_x max_y x y = filter (\(x,y) -> x >= 0 && x <= max_x && y >= 0 && y <= max_y) [(x-1, y), (x+1, y), (x, y-1), (x, y+1)]
+
+mapInd :: (Int -> a -> b) -> [a] -> [b]
+mapInd f = zipWith f [0..]
+
+minMaybe :: [Maybe Int] -> Maybe Int
+minMaybe = foldr go Nothing where
+    go Nothing state = state
+    go (Just x) Nothing = Just x
+    go (Just x) (Just y) = Just (min x y)
+
+searchStep :: Array (Int,Int) Int -> Array (Int,Int) (Maybe Int) -> [(Int,Int)] -> (Array (Int,Int) (Maybe Int), [(Int,Int)])
+searchStep costs so_far active = (so_far // updates, map fst updates) where
+    updates = mapMaybe (\(x,y) -> let cur = so_far ! (x,y); new = minMaybe (cur:neigh_costs x y); in if cur /= new then Just ((x,y), new) else Nothing) new_active
+    new_active = nub $ sort $ concatMap (uncurry n) active
+    n = uncurry neighs (snd $ bounds costs)
+    neigh_costs x y = map (\(x',y') -> fmap (+ (costs ! (x,y))) (so_far !(x',y')) ) (n x y)
+
+search :: [[Int]] -> Int
+search cavern = fromJust $ final_iter ! snd (bounds final_iter) where
+    iters = iterate (\(i,(s,a)) -> trace ("step " ++ show i ++ show (s ! snd (bounds s))) (i+1, searchStep cavern_array s a)) (0,(init_array, [(0,0)]))
+    final_iter = fst $ snd $ iters !! (10 + length cavern + length (head cavern))
+    -- search' :: [[Int]] -> [[Maybe Int]] -> Int
+    -- search' cavern step = iterate (searchStep cavern) init
+    -- search' cavern step = case last $ last s of
+    --     Nothing -> trace "Nothing yet.." $ search' cavern s
+    --     Just x -> if Just x <= last (last $ searchStep cavern s) then x else trace ("test; " ++ show x ++ " > " ++ show (last(last $ searchStep cavern s))) $ search' cavern s
+    --     where s = searchStep cavern step
+    toArray = Data.Array.listArray ((0,0), (length cavern - 1, length (head cavern) - 1))
+    cavern_array = toArray $ concat cavern
+    firstLine = Just 0: replicate (length cavern - 1) Nothing
+    init = firstLine : map (map (const Nothing)) (tail cavern)
+    init_array = toArray $ concat init
+
+fullMap :: [[Int]] -> [[Int]]
+fullMap cavern = full where
+    increment 9 = 1
+    increment x = x + 1
+    first_row = map (concat . take 5 . iterate (map increment)) cavern
+    full = concat $ take 5 $ iterate (map (map increment)) first_row
+
+
+
+main :: IO ()
+main = do
+    cavern <- map (map digitToInt) . lines <$> getContents
+    putStr "part 1: "
+    print $ search cavern
+
+    putStr "part 2: "
+    -- print cavern
+    -- mapM_ print $ fullMap cavern
+    print $ search $ fullMap cavern
+
+    print "bye"
\ No newline at end of file
diff --git a/2021/day16.hs b/2021/day16.hs
new file mode 100644
index 0000000..b3afaf0
--- /dev/null
+++ b/2021/day16.hs
@@ -0,0 +1,85 @@
+module Main where
+import Data.List (foldl', unfoldr)
+import Debug.Trace (traceShow)
+
+type Packet = [Bool]
+data Length = Bits Int | Count Int deriving Show
+data DecodedPacket = Lit Int Int Int | Op Int Int Length [DecodedPacket] deriving Show
+
+binToDec :: [Bool] -> Int
+binToDec = foldl' (\acc x -> acc * 2 + fromEnum x) 0
+
+decodeHex :: Char -> Packet
+decodeHex '0' = map toEnum [0, 0, 0, 0]
+decodeHex '1' = map toEnum [0, 0, 0, 1]
+decodeHex '2' = map toEnum [0, 0, 1, 0]
+decodeHex '3' = map toEnum [0, 0, 1, 1]
+decodeHex '4' = map toEnum [0, 1, 0, 0]
+decodeHex '5' = map toEnum [0, 1, 0, 1]
+decodeHex '6' = map toEnum [0, 1, 1, 0]
+decodeHex '7' = map toEnum [0, 1, 1, 1]
+decodeHex '8' = map toEnum [1, 0, 0, 0]
+decodeHex '9' = map toEnum [1, 0, 0, 1]
+decodeHex 'A' = map toEnum [1, 0, 1, 0]
+decodeHex 'B' = map toEnum [1, 0, 1, 1]
+decodeHex 'C' = map toEnum [1, 1, 0, 0]
+decodeHex 'D' = map toEnum [1, 1, 0, 1]
+decodeHex 'E' = map toEnum [1, 1, 1, 0]
+decodeHex 'F' = map toEnum [1, 1, 1, 1]
+decodeHex x = []
+
+buildPacket :: [Bool] -> [(DecodedPacket, [Bool])]
+buildPacket p = unfoldr go p where
+    go [] = Nothing
+    go p = Just ((dec, next), next) where (dec,next) = decode p
+
+decode :: Packet -> (DecodedPacket, [Bool])
+decode p = decode' typeID $ drop 6 p where
+    version = binToDec $ take 3 p
+    typeID = binToDec $ take 3 $ drop 3 p
+
+    decodeLit :: [Bool] -> ([Bool], [Bool])
+    decodeLit [] = error "trying to decode an empty list"
+    decodeLit (False:ps) = splitAt 4 ps
+    decodeLit (True:ps)  = let (next,rem) = decodeLit (drop 4 ps) in (take 4 ps ++ next, rem)
+    decode' :: Int -> [Bool] -> (DecodedPacket, [Bool])
+    decode' 4 p = let (num, rem) = decodeLit p in (Lit version typeID (binToDec num), rem)
+    decode' x [] = error "unexpected end-of-packet"
+    decode' x (False:ps) = (Op version typeID (Bits numBits) ourPackets, next) where
+        numBits = binToDec $ take 15 ps
+        (this,next) = splitAt numBits $ drop 15 ps
+        ourPackets = map fst $ buildPacket this
+    decode' x (True:ps) = (Op version typeID (Count numPackets) (map fst ourPackets), remainder) where
+        numPackets = binToDec $ take 11 ps
+        ourPackets = take numPackets $ buildPacket $ drop 11 ps
+        remainder = snd $ last ourPackets
+
+versionSum :: DecodedPacket -> Int
+versionSum (Lit v t x) = v
+versionSum (Op v t l ps) = v + sum (map versionSum ps)
+
+evalPacket :: DecodedPacket -> Int 
+evalPacket (Lit v t x) = x
+evalPacket (Op v 0 l ps) = sum $ map evalPacket ps
+evalPacket (Op v 1 l ps) = product $ map evalPacket ps
+evalPacket (Op v 2 l ps) = minimum $ map evalPacket ps
+evalPacket (Op v 3 l ps) = maximum $ map evalPacket ps
+evalPacket (Op v 5 l (x:y:xs)) = fromEnum $ evalPacket x > evalPacket y
+evalPacket (Op v 6 l (x:y:xs)) = fromEnum $ evalPacket x < evalPacket y
+evalPacket (Op v 7 l (x:y:xs)) = fromEnum $ evalPacket x == evalPacket y
+evalPacket x = error $ "invalid packet: " ++ show x
+
+
+main :: IO ()
+main = do
+    input <- concatMap decodeHex <$> getContents
+    let packet = fst $ decode input
+    print packet
+    
+    putStr "part 1: "
+    print $ versionSum packet
+
+    putStr "part 2: "
+    print $ evalPacket packet
+
+    print "bye"
\ No newline at end of file