diff --git a/src/AOC/Challenge/Day24.hs b/src/AOC/Challenge/Day24.hs
index 26badce..eb02ac4 100644
--- a/src/AOC/Challenge/Day24.hs
+++ b/src/AOC/Challenge/Day24.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS_GHC -Wno-unused-imports   #-}
+{-# OPTIONS_GHC -Wno-unused-imports #-}
 {-# OPTIONS_GHC -Wno-unused-top-binds #-}
 
 -- |
@@ -20,41 +20,154 @@
 --     types @_ :~> _@ with the actual types of inputs and outputs of the
 --     solution.  You can delete the type signatures completely and GHC
 --     will recommend what should go in place of the underscores.
+module AOC.Challenge.Day24
+  ( day24a,
+    day24b,
+  )
+where
 
-module AOC.Challenge.Day24 (
-    -- day24a
-  -- , day24b
-  ) where
+import AOC.Prelude
+import qualified Data.Graph.Inductive as G
+import qualified Data.IntMap as IM
+import qualified Data.IntSet as IS
+import qualified Data.List.NonEmpty as NE
+import qualified Data.List.PointedList as PL
+import qualified Data.List.PointedList.Circular as PLC
+import qualified Data.Map as M
+import qualified Data.OrdPSQ as PSQ
+import qualified Data.Sequence as Seq
+import qualified Data.Set as S
+import qualified Data.Text as T
+import qualified Data.Vector as V
+import qualified Linear as L
+import qualified Text.Megaparsec as P
+import qualified Text.Megaparsec.Char as P
+import qualified Text.Megaparsec.Char.Lexer as PP
 
-import           AOC.Prelude
+-- 213004023520250, 255007063487325, 286351797522218 @ 118, 41, -64
 
-import qualified Data.Graph.Inductive           as G
-import qualified Data.IntMap                    as IM
-import qualified Data.IntSet                    as IS
-import qualified Data.List.NonEmpty             as NE
-import qualified Data.List.PointedList          as PL
-import qualified Data.List.PointedList.Circular as PLC
-import qualified Data.Map                       as M
-import qualified Data.OrdPSQ                    as PSQ
-import qualified Data.Sequence                  as Seq
-import qualified Data.Set                       as S
-import qualified Data.Text                      as T
-import qualified Data.Vector                    as V
-import qualified Linear                         as L
-import qualified Text.Megaparsec                as P
-import qualified Text.Megaparsec.Char           as P
-import qualified Text.Megaparsec.Char.Lexer     as PP
-
-day24a :: _ :~> _
-day24a = MkSol
-    { sParse = Just . lines
-    , sShow  = show
-    , sSolve = Just
+type Point3 = V3 Int
+
+collision ::
+  forall f.
+  (Show (f (Maybe Rational)), Show (f Int), Num (f Int), Applicative f, Num (f Rational), Foldable f) =>
+  V2 (f Int) ->
+  V2 (f Int) ->
+  Maybe (f Rational)
+collision p1@(V2 r1 v1) p2@(V2 r2 v2) = traceShow (p1, p2) do
+  Just t' <- allSame t
+  pure $ (fromIntegral <$> r1) + t' *^ (fromIntegral <$> v1)
+  where
+    t :: f (Maybe Rational)
+    t = traceShowId $ liftA2 maybeDivide (r2 - r1) (v2 - v1)
+
+-- r_1 + t v_1 = r_2 + t v_2
+-- t (v1 - v2) = r2 - r1
+--
+-- t = (r2x - r1x) / (v1x - v2x)
+
+-- lineIntersect :: forall f. (Show (f (Maybe Rational)), Show (f Int), Num (f Int), Applicative f, Num (f Rational), Foldable f)
+--                 => V2 (f Int) -> V2 (f Int) -> Maybe (f Rational)
+-- lineIntersect p1@(V2 r1 v1) p2@(V2 r2 v2) = traceShow (p1,p2) do
+--   Just t' <- allSame t
+--   pure $ (fromIntegral <$> r1) + t' *^ (fromIntegral <$> v1)
+--   where
+--     t :: f (Maybe Rational)
+--     t = traceShowId $ liftA2 maybeDivide (r2 - r1) (v2 - v1)
+
+-- r_1 + t_1 v_1 = r_2 + t_2 v_2
+--
+-- 2 unknowns, 3 eqs
+-- r1x + t1 v1x = r2x + t2 v2x
+-- r1y + t1 v1y = r2y + t2 v2y
+-- r1z + t1 v1z = r2z + t2 v2z
+--
+--   v1x t1  -v2x t2 = r2x - r1x
+--   v1y t1  -v2y t2 = r2y - r1y
+--   v1z t1  -v2z t2 = r2z - r1z
+--
+--       t1 - v2x/v1x t2 = (r2x - r1x)/v1x
+--       t1 - v2y/v1y t2 = (r2y - r1y)/v1y
+--       t1 - v2z/v1z t2 = (r2z - r1z)/v1z
+--
+--       t1 - v2x/v1x t2 = (r2x - r1x)/v1x
+--          - v2y/v1y t2 = (r2y - r1y)/v1y - (r2x - r1x)/v1x
+--       t1 - v2z/v1z t2 = (r2z - r1z)/v1z
+--
+-- wait lol in our case it's only two eqs
+-- r1x + t1 v1x = r2x + t2 v2x
+-- r1y + t1 v1y = r2y + t2 v2y
+--
+--   v1x t1  -v2x t2 = r2x - r1x
+--   v1y t1  -v2y t2 = r2y - r1y
+--
+--       t1 - v2x/v1x t2 = (r2x - r1x)/v1x
+--       t1 - v2y/v1y t2 = (r2y - r1y)/v1y
+--
+--       t1 - v2x/v1x t2 = (r2x - r1x)/v1x
+--          (v2x/v1x - v2y/v1y) t2 = (r2y - r1y)/v1y - (r2x - r1x)/v1x
+--          t2 = ((r2y - r1y)/v1y - (r2x - r1x)/v2x)
+--                  / (v2x/v1x - v2y/v1y)
+--
+--       t1 = (r2x - r1x)/v1x + v2x/v1x t2 
+
+intersect2d :: V2 Point -> V2 Point -> Maybe (V2 Rational)
+intersect2d p1@(V2 (V2 rx1 ry1) (V2 vx1 vy1)) p2@(V2 (V2 rx2 ry2) (V2 vx2 vy2)) = traceShow (p1,p2) . traceShowId $ do
+  a <- maybeDivide (ry2 - ry1) vy1
+  b <- maybeDivide (rx2 - rx1) vx1
+  c <- maybeDivide vx2 vx1
+  d <- maybeDivide vy2 vy1
+  guard $ (c - d) /= 0
+  let t2 = (a - b) / (c - d)
+      t1 = b + t2 * c
+  guard $ t2 > 0
+  guard $ t1 > 0
+  pure $ V2 (fromIntegral rx2 + t2 * fromIntegral vx2) (fromIntegral ry2 + t2 * fromIntegral vy2)
+
+maybeDivide :: Int -> Int -> Maybe Rational
+maybeDivide x y
+  | y == 0 = Nothing
+  | otherwise = Just $ fromIntegral x / fromIntegral y
+
+allSame :: (Eq a, Foldable f) => f a -> Maybe a
+allSame xs = case toList xs of
+  [] -> Nothing
+  y : ys
+    | all (== y) ys -> Just y
+    | otherwise -> Nothing
+
+day24a :: [V2 (V3 Int)] :~> _
+day24a =
+  MkSol
+    { sParse =
+        traverse
+          ( traverse (traverse readMaybe <=< listV3 . splitOn ",")
+              <=< listV2
+              . splitOn "@"
+          )
+          . lines,
+      sShow = show,
+      sSolve =
+        noFail $ \ps ->
+          let inRange =
+                all \q ->
+                  q >= fromIntegral @Int (dyno_ "mn" 200000000000000)
+                    && q <= fromIntegral @Int (dyno_ "mx" 400000000000000)
+           in countTrue inRange $
+                traceShowId
+                  [ p
+                    | x : ys <- fmap (fmap (view _xy)) <$> tails ps,
+                      y <- ys,
+                      p <- maybeToList $ intersect2d x y
+                  ]
     }
 
 day24b :: _ :~> _
-day24b = MkSol
-    { sParse = sParse day24a
-    , sShow  = show
-    , sSolve = Just
+day24b =
+  MkSol
+    { sParse = sParse day24a,
+      sShow = show,
+      sSolve =
+        noFail $
+          id
     }
diff --git a/test-data/2023/24a.txt b/test-data/2023/24a.txt
new file mode 100644
index 0000000..2401ea0
--- /dev/null
+++ b/test-data/2023/24a.txt
@@ -0,0 +1,8 @@
+19, 13, 30 @ -2,  1, -2
+18, 19, 22 @ -1, -1, -2
+20, 25, 34 @ -2, -2, -4
+12, 31, 28 @ -1, -2, -1
+20, 19, 15 @  1, -5, -3
+>>>mn:7:int
+>>>mx:27:int
+>>> 2