diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e802c2..5f1e8b8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog for profold
 
+## Upcoming
+* clean up code
+* document functions
+
 ## 1.0.0.0
 * add readme
 * create project
diff --git a/app/Main.hs b/app/Main.hs
index 661bcd2..a3e198a 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE OverloadedStrings #-}
-
 module Main where
 
 import           Brick
@@ -11,14 +9,11 @@ import           Profold.App
 import           Profold.Options
 import           Profold.ParseProfFile
 
-data UiName = UiViewport
-  deriving (Show, Eq, Ord)
-
 main :: IO ()
 main = do
   opts <- execParser options
   let filename = optFileName opts
   text <- T.readFile filename
   case parseProfFile filename text of
-    Left e     -> putStrLn e
+    Left e  -> putStrLn e
     Right f -> void $ defaultMain myApp $ newUiState (profInfoLines f) (profNode f)
diff --git a/src/Profold/App.hs b/src/Profold/App.hs
index 5d346f2..b79f3d4 100644
--- a/src/Profold/App.hs
+++ b/src/Profold/App.hs
@@ -1,7 +1,10 @@
 {-# LANGUAGE OverloadedStrings #-}
 
+-- | This module implements a brick application for browsing a 'LineNode' tree.
+
 module Profold.App
   ( UiState
+  , UiName
   , newUiState
   , myApp
   ) where
@@ -14,16 +17,24 @@ import qualified Graphics.Vty       as Vty
 
 import           Profold.LineNode
 
+-- | Unique names for UI elements used in this application.
 data UiName = UiList
   deriving (Show, Eq, Ord)
 
+-- | The state for the brick application.
 data UiState = UiState
   { uiInfo :: [T.Text]
   , uiTree :: LineNode
   , uiList :: List UiName (Path, LineNode)
   } deriving (Show)
 
-newUiState :: [T.Text] -> LineNode -> UiState
+-- | Create an initial ui state.
+newUiState
+  :: [T.Text]
+  -- ^ A list of lines which should contain the column labels. These lines will always be displayed at the top of the screen.
+  -> LineNode
+  -- ^ The tree to display.
+  -> UiState
 newUiState info ln = toggleFold $ UiState info ln $ list UiList (flatten ln) 1
 
 toggleFold :: UiState -> UiState
@@ -74,6 +85,7 @@ myAttrMap = attrMap Vty.defAttr
   , ("info", Vty.defAttr `Vty.withStyle` Vty.reverseVideo)
   ]
 
+-- | The brick application.
 myApp :: App UiState () UiName
 myApp = App
   { appDraw         = myAppDraw
diff --git a/src/Profold/LineNode.hs b/src/Profold/LineNode.hs
index b07dab5..09aeaae 100644
--- a/src/Profold/LineNode.hs
+++ b/src/Profold/LineNode.hs
@@ -1,3 +1,6 @@
+-- | A module containing the tree data structure for lines in the @.prof@ file
+-- and some useful functions.
+
 module Profold.LineNode
   ( LineNode(..)
   , newLineNode
@@ -6,20 +9,30 @@ module Profold.LineNode
   , modify
   ) where
 
-import qualified Data.Text    as T
-import qualified Data.Vector  as V
+import qualified Data.Text   as T
+import qualified Data.Vector as V
 
+-- | A line from the @.prof@ file and its children.
 data LineNode = LineNode
   { lineText     :: T.Text
+  -- ^ The complete text of the line, including its indentation.
   , lineChildren :: V.Vector LineNode
+  -- ^ The line's children.
   , lineFolded   :: Bool
+  -- ^ Whether the line's children are folded away.
   } deriving (Show)
 
+-- | Create a new 'LineNode'.
 newLineNode :: T.Text -> [LineNode] -> LineNode
 newLineNode text children = LineNode text (V.fromList children) True
 
+-- | A path (similar to a file path) referencing a node inside a 'LineNode'
+-- tree.
 type Path = [Int]
 
+-- | Convert a 'LineNode' into a flat list of itself and all visible children.
+-- The list includes the 'Path' to each node. Nodes that would not be visible
+-- because one of their parents is folded are not included.
 flatten :: LineNode -> V.Vector (Path, LineNode)
 flatten ln
   | lineFolded ln = V.singleton ([], ln)
@@ -34,6 +47,8 @@ modifyAtIndex :: Int -> (a -> a) -> V.Vector a -> V.Vector a
 -- Yes, this function looks ugly, but it's short enough that I don't care.
 modifyAtIndex i f v = maybe v (\a -> v V.// [(i, f a)]) (v V.!? i)
 
+-- | Modify a node at a specific location in the tree. Returns the original node
+-- if no node exists at that path.
 modify :: (LineNode -> LineNode) -> Path -> LineNode -> LineNode
 modify f [] ln = f ln
 modify f (i:is) ln =
diff --git a/src/Profold/Options.hs b/src/Profold/Options.hs
index 9d3b10e..64ee926 100644
--- a/src/Profold/Options.hs
+++ b/src/Profold/Options.hs
@@ -1,3 +1,5 @@
+-- | A module for parsing command line options.
+
 module Profold.Options
   ( Options(..)
   , options
@@ -5,13 +7,16 @@ module Profold.Options
 
 import Options.Applicative
 
+-- | The command line options.
 newtype Options = Options
   { optFileName :: String
+  -- ^ Name of the @.prof@ file to open and parse.
   } deriving (Show)
 
 parser :: Parser Options
 parser = Options
   <$> strArgument (help "Path to the .prof file" <> metavar "FILE")
 
+-- | A parser for the command line options.
 options :: ParserInfo Options
 options = info (helper <*> parser) fullDesc
diff --git a/src/Profold/ParseProfFile.hs b/src/Profold/ParseProfFile.hs
index bf3809d..c7412cb 100644
--- a/src/Profold/ParseProfFile.hs
+++ b/src/Profold/ParseProfFile.hs
@@ -1,5 +1,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 
+-- | This module contains a parser for parsing @.prof@ files.
+
 module Profold.ParseProfFile
   ( ProfFile(..)
   , parseProfFile
@@ -13,6 +15,8 @@ import           Text.Megaparsec.Char
 
 import           Profold.LineNode
 
+-- | A @.prof@ file includes a few lines at the beginning that contain the
+-- column names.
 data ProfFile = ProfFile
   { profInfoLines :: [T.Text]
   , profNode      :: LineNode
@@ -48,6 +52,8 @@ profFile = do
   node <- lineNode ""
   pure $ ProfFile info node
 
+-- | A parser for @.prof@ files. If the file could not be parsed, returns a
+-- @Left errorMessage@.
 parseProfFile :: String -> T.Text -> Either String ProfFile
 parseProfFile filename text = case parse profFile filename text of
   Left e   -> Left $ errorBundlePretty e