diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright John Ky (c) 2016-2019
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Author name here nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# rebounds
+
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/hw-playground-linear.cabal b/hw-playground-linear.cabal
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--- /dev/null
+++ b/hw-playground-linear.cabal
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+cabal-version: 2.4
+
+name:                   hw-playground-linear
+version:                0.1.0.0
+synopsis:               Primitive functions and data types
+description:            Primitive functions and data types.
+category:               Data
+stability:              Experimental
+homepage:               http://github.com/haskell-works/hw-playground-linear#readme
+bug-reports:            https://github.com/haskell-works/hw-playground-linear/issues
+author:                 John Ky
+maintainer:             newhoggy@gmail.com
+copyright:              2016-2020 John Ky
+license:                BSD-3-Clause
+license-file:           LICENSE
+tested-with:            GHC == 8.10.2, GHC == 8.8.3, GHC == 8.6.5, GHC == 8.4.4
+build-type:             Simple
+extra-source-files:     README.md
+
+source-repository head
+  type: git
+  location: https://github.com/haskell-works/hw-playground-linear
+
+common base                       { build-depends: base                       >= 4.11       && < 5      }
+
+common generic-lens               { build-depends: generic-lens               >= 1.2.0.1    && < 2.1    }
+common hedgehog                   { build-depends: hedgehog                   >= 0.5        && < 1.1    }
+common hmatrix                    { build-depends: hmatrix                    >= 0.20.0.0   && < 0.21   }
+common hmatrix-csv                { build-depends: hmatrix-csv                >= 0.1.0.2    && < 0.2    }
+common hspec                      { build-depends: hspec                      >= 2.4        && < 2.8    }
+common hw-hspec-hedgehog          { build-depends: hw-hspec-hedgehog          >= 0.1        && < 0.2    }
+common lens                       { build-depends: lens                       >= 4          && < 5      }
+common optparse-applicative       { build-depends: optparse-applicative       >= 0.14       && < 0.17   }
+common text                       { build-depends: text                       >= 1.2        && < 1.3    }
+
+common config
+  default-language:     Haskell2010
+
+common hw-playground-linear
+  build-depends:        hw-playground-linear
+
+library
+  import:               base
+                      , config
+                      , hmatrix
+                      , hmatrix-csv
+                      , text
+  exposed-modules:      HaskellWorks.Playground.Linear
+  other-modules:        Paths_hw_playground_linear
+  autogen-modules:      Paths_hw_playground_linear
+  hs-source-dirs:       src
+
+test-suite hw-playground-linear-test
+  import:               base
+                      , config
+                      , hedgehog
+                      , hspec
+                      , hw-hspec-hedgehog
+                      , hw-playground-linear
+  type:                 exitcode-stdio-1.0
+  main-is:              Spec.hs
+  other-modules:        HaskellWorks.Playground.LinearSpec
+                        Paths_hw_playground_linear
+  autogen-modules:      Paths_hw_playground_linear
+  build-depends:        hw-playground-linear
+  hs-source-dirs:       test
+  ghc-options:          -threaded -rtsopts -with-rtsopts=-N
+  build-tool-depends:   hspec-discover:hspec-discover
diff --git a/src/HaskellWorks/Playground/Linear.hs b/src/HaskellWorks/Playground/Linear.hs
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--- /dev/null
+++ b/src/HaskellWorks/Playground/Linear.hs
@@ -0,0 +1,10 @@
+module HaskellWorks.Playground.Linear where
+
+import Numeric.LinearAlgebra
+import Prelude               hiding ((<>))
+
+variance :: Matrix Double -> Matrix Double
+variance m = x <> ((m - asRow rdMean) ** 2)
+  where (rdMean, _) = meanCov m
+        r = rows m
+        x = konst (1 / fromIntegral r) (1, r)
diff --git a/test/HaskellWorks/Playground/LinearSpec.hs b/test/HaskellWorks/Playground/LinearSpec.hs
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--- /dev/null
+++ b/test/HaskellWorks/Playground/LinearSpec.hs
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+{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+
+module HaskellWorks.Playground.LinearSpec (spec) where
+
+import HaskellWorks.Hspec.Hedgehog
+import Hedgehog
+import Test.Hspec
+
+import qualified Hedgehog.Gen   as G
+import qualified Hedgehog.Range as R
+
+{-# ANN module ("HLint: Ignore Redundant do" :: String) #-}
+{-# ANN module ("HLint: Ignore Reduce duplication"  :: String) #-}
+
+spec :: Spec
+spec = describe "HaskellWorks.LinearSpec" $ do
+  it "Stub" $ requireProperty $ do
+    True === True
diff --git a/test/Spec.hs b/test/Spec.hs
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--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1,1 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}
