diff --git a/Graphics/Web/Processing/Core/Interface.hs b/Graphics/Web/Processing/Core/Interface.hs
--- a/Graphics/Web/Processing/Core/Interface.hs
+++ b/Graphics/Web/Processing/Core/Interface.hs
@@ -41,6 +41,12 @@
    , resetMatrix
    -- * Mouse
    , getMousePoint
+   -- * Keyboard
+   , Key (..)
+   , ArrowKey (..)
+   , KeyModifier (..)
+   , SpecialKey (..)
+   , matchKey
    -- * Conditionals
    , iff
    -- * Others
@@ -54,7 +60,9 @@
 -- Internal
 import Graphics.Web.Processing.Core.Primal
 import Graphics.Web.Processing.Core.Monad
-import Graphics.Web.Processing.Core.Var (readVar)
+import Graphics.Web.Processing.Core.Var (writeVar,readVar)
+--
+import Control.Arrow (first)
 
 ---- PREDEFINED VALUES
 
@@ -289,6 +297,64 @@
  x <- readVar $ varFromText "mouseX"
  y <- readVar $ varFromText "mouseY"
  return (x,y)
+
+---- KEYBOARD
+
+-- | Keyboard keys recognized by Processing.
+data Key =
+    CharKey Char
+  | SpecialKey SpecialKey
+  | ArrowKey ArrowKey
+  | ModKey KeyModifier Key
+
+-- | Arrow keys.
+data ArrowKey = UP | DOWN | LEFT | RIGHT
+
+-- | Key modifiers.
+data KeyModifier = ALT | CONTROL | SHIFT
+
+-- | Special keys.
+data SpecialKey =
+    BACKSPACE
+  | TAB
+  | ENTER
+  | RETURN
+  | ESC
+
+--                      CODED                   UNCODED
+keySplit :: Key -> ([Proc_KeyCode],Maybe (Either Proc_Key Proc_KeyCode))
+keySplit (CharKey c) = ([],Just $ Left $ Key_Char c)
+keySplit (SpecialKey BACKSPACE) = ([],Just $ Right $ KeyCode_BACKSPACE)
+keySplit (SpecialKey TAB) = ([],Just $ Right $ KeyCode_TAB)
+keySplit (SpecialKey ENTER) = ([],Just $ Right $ KeyCode_ENTER)
+keySplit (SpecialKey RETURN) = ([],Just $ Right $ KeyCode_RETURN)
+keySplit (SpecialKey ESC) = ([],Just $ Right $ KeyCode_ESC)
+keySplit (ArrowKey UP) = ([KeyCode_UP], Nothing)
+keySplit (ArrowKey DOWN) = ([KeyCode_DOWN], Nothing)
+keySplit (ArrowKey LEFT) = ([KeyCode_LEFT], Nothing)
+keySplit (ArrowKey RIGHT) = ([KeyCode_RIGHT], Nothing)
+keySplit (ModKey m k) =
+  let modToKeyCode :: KeyModifier -> Proc_KeyCode
+      modToKeyCode ALT = KeyCode_ALT
+      modToKeyCode CONTROL = KeyCode_CONTROL
+      modToKeyCode SHIFT = KeyCode_SHIFT
+  in  first (modToKeyCode m:) $ keySplit k
+
+-- | This function takes a variable of type 'Proc_Bool' and a 'Key', and sets the variable to
+--   'true' if the key pressed is the given 'Key'. Otherwise, the variable is set to 'false'.
+matchKey :: (ProcMonad m, Monad (m KeyPressed)) => Var Proc_Bool -> Key -> m KeyPressed ()
+matchKey v k = do
+  let (codedKeys,uncodedKey) = keySplit k
+  if null codedKeys
+     then return ()
+     else iff (Key_Var #== Key_CODED)
+              (writeVar v $ foldr1 (#&&) $ fmap (KeyCode_Var #==) codedKeys)
+              (writeVar v false)
+  b <- readVar v
+  case uncodedKey of
+    Nothing -> return ()
+    Just (Left  pk) -> writeVar v $ Key_Var     #== pk #&& b
+    Just (Right ck) -> writeVar v $ KeyCode_Var #== ck #&& b
 
 ---- SETUP
 
diff --git a/Graphics/Web/Processing/Core/Primal.hs b/Graphics/Web/Processing/Core/Primal.hs
--- a/Graphics/Web/Processing/Core/Primal.hs
+++ b/Graphics/Web/Processing/Core/Primal.hs
@@ -10,9 +10,10 @@
   --   use of certain commands to specific contexts.
     Preamble (..), Setup (..), Draw (..)
   , MouseClicked (..), MouseReleased (..)
-  -- ** Processing types
+  , KeyPressed (..)
+  -- ** @Proc_*@ types
   -- *** Boolean
-  , Proc_Bool, fromBool
+  , Proc_Bool (..), fromBool
   , true, false
   , pnot, (#||), (#&&)
   -- *** Int
@@ -29,6 +30,9 @@
   , Proc_Char , fromChar
   -- *** Text
   , Proc_Text, fromStText
+  -- *** Keys
+  , Proc_Key (..)
+  , Proc_KeyCode (..)
   -- ** Type class of proc types
   , ProcType (..)
   -- ** Conditionals
@@ -85,6 +89,9 @@
 -- | Code that is executed when the mouse is released.
 data MouseReleased = MouseReleased
 
+-- | Code executed when a key is pressed.
+data KeyPressed = KeyPressed
+
 -- PRETTY-HELPERS
 
 pfunction :: Text -> [Doc] -> Doc
@@ -145,7 +152,12 @@
    | Char_NEq Proc_Char Proc_Char
      -- Text
    | Text_Eq Proc_Text Proc_Text
-     deriving Eq
+     -- Key
+   | Key_Eq Proc_Key Proc_Key
+   | KeyCode_Eq Proc_KeyCode Proc_KeyCode
+   -- Conditional
+ | Bool_Cond Proc_Bool Proc_Bool Proc_Bool
+     deriving (Eq,Ord)
 
 instance Extended Bool Proc_Bool where
  extend True  = Proc_True 
@@ -174,6 +186,9 @@
 docG :: Doc
 docG = fromText ">"
 
+docCond :: Doc -> Doc -> Doc -> Doc
+docCond _if _then _else = _if <+> fromText "?" <+> _then <+> fromText ":" <+> _else
+
 indentLevel :: Int
 indentLevel = 3
 
@@ -202,6 +217,9 @@
  ppr (Char_Eq x y) = parens $ ppr x <+> docEq <+> ppr y
  ppr (Char_NEq x y) = parens $ ppr x <+> docNEq <+> ppr y
  ppr (Text_Eq x y) = ppr x <> fromText "." <> pfunction "equals" [ppr y]
+ ppr (Key_Eq x y) = parens $ ppr x <+> docEq <+> ppr y
+ ppr (KeyCode_Eq x y) = parens $ ppr x <+> docEq <+> ppr y
+ ppr (Bool_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Value of 'True'.
 true :: Proc_Bool
@@ -245,6 +263,8 @@
    -- Functions
  | Int_Abs Proc_Int
  | Int_Floor Proc_Float
+   -- Conditional
+ | Int_Cond Proc_Bool Proc_Int Proc_Int
    deriving Eq
 
 instance Extended Int Proc_Int where
@@ -262,6 +282,7 @@
  ppr (Int_Var t) = fromText t
  ppr (Int_Abs n) = pfunction "abs" [ppr n]
  ppr (Int_Floor x) = pfunction "floor" [ppr x]
+ ppr (Int_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Cast an 'Int' value.
 fromInt :: Int -> Proc_Int
@@ -333,6 +354,8 @@
  | Float_Floor Proc_Float -- Applies floor but it treats the result
                           -- as a float. Only internal.
  | Float_Noise Proc_Float Proc_Float
+   -- Conditional
+ | Float_Cond Proc_Bool Proc_Float Proc_Float
    deriving (Eq,Ord)
 
 instance Extended Float Proc_Float where
@@ -359,6 +382,7 @@
 recFloat f (Float_Arctangent x) = Float_Arctangent $ f x
 recFloat f (Float_Floor x) = Float_Floor $ f x
 recFloat f (Float_Noise x y) = Float_Noise (f x) (f y)
+recFloat f (Float_Cond b x y) = Float_Cond b (f x) (f y)
 recFloat _ x = x
 
 instance Pretty Proc_Float where 
@@ -380,6 +404,7 @@
  ppr (Float_Arctangent x) = pfunction "atan" [ppr x]
  ppr (Float_Floor x) = pfunction "floor" [ppr x]
  ppr (Float_Noise x y) = pfunction "noise" [ppr x,ppr y]
+ ppr (Float_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Cast a 'Float' value.
 fromFloat :: Float -> Proc_Float
@@ -400,6 +425,7 @@
 intToFloat (Int_Var t) = Float_Var t
 intToFloat (Int_Abs n) = Float_Abs $ intToFloat n
 intToFloat (Int_Floor x) = Float_Floor x
+intToFloat (Int_Cond b x y) = Float_Cond b (intToFloat x) (intToFloat y)
 
 -- | WARNING: 'signum' method is undefined.
 instance Num Proc_Float where
@@ -434,16 +460,21 @@
  atanh = error "Proc_Float: atanh method is undefined."
 
 -- | Type of images.
-data Proc_Image = Image_Var Text deriving Eq
+data Proc_Image =
+   Image_Var Text
+ | Image_Cond Proc_Bool Proc_Image Proc_Image
+   deriving Eq
 
 instance Pretty Proc_Image where
  ppr (Image_Var t) = fromText t
+ ppr (Image_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Type of characters.
 data Proc_Char =
    Proc_Char Char
  | Char_Var Text
-   deriving Eq
+ | Char_Cond Proc_Bool Proc_Char Proc_Char
+   deriving (Eq,Ord)
 
 instance Extended Char Proc_Char where
  extend = Proc_Char
@@ -457,12 +488,15 @@
 instance Pretty Proc_Char where
  ppr (Proc_Char c) = enclose squote squote (char c)
  ppr (Char_Var n) = fromText n
+ ppr (Char_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Type of textual values.
 data Proc_Text =
    Proc_Text Text
  | Text_Var Text
-   deriving Eq
+   -- Conditional
+ | Text_Cond Proc_Bool Proc_Text Proc_Text
+   deriving (Eq,Ord)
 
 instance Extended Text Proc_Text where
  extend = Proc_Text
@@ -470,8 +504,11 @@
  patmatch _ = Nothing
 
 instance Pretty Proc_Text where
+ -- Wrong pretty-printer for text values. Fix it to
+ -- escape characters.
  ppr (Proc_Text t) = enclose dquote dquote (fromText t)
  ppr (Text_Var n) = fromText n
+ ppr (Text_Cond b x y) = parens $ docCond (ppr b) (ppr x) (ppr y)
 
 -- | Cast a strict 'Text' value.
 fromStText :: Text -> Proc_Text
@@ -480,6 +517,52 @@
 instance IsString Proc_Text where
  fromString = fromStText . fromString
 
+-- | Type of keyboard keys.
+data Proc_Key =
+   Key_Var
+ | Key_CODED
+ | Key_Char Char
+   deriving (Eq,Ord)
+
+instance Pretty Proc_Key where
+ ppr Key_Var = fromText "key"
+ ppr Key_CODED = fromText "CODED"
+ ppr (Key_Char c) = ppr $ fromChar c
+
+-- | Type of keyboard key codes.
+data Proc_KeyCode =
+   KeyCode_Var
+ | KeyCode_UP
+ | KeyCode_DOWN
+ | KeyCode_LEFT
+ | KeyCode_RIGHT
+ | KeyCode_ALT
+ | KeyCode_CONTROL
+ | KeyCode_SHIFT
+ | KeyCode_BACKSPACE
+ | KeyCode_TAB
+ | KeyCode_ENTER
+ | KeyCode_RETURN
+ | KeyCode_ESC
+ | KeyCode_DELETE
+   deriving (Eq,Ord)
+
+instance Pretty Proc_KeyCode where
+ ppr KeyCode_Var = fromText "keyCode"
+ ppr KeyCode_UP = fromText "UP"
+ ppr KeyCode_DOWN = fromText "DOWN"
+ ppr KeyCode_LEFT = fromText "LEFT"
+ ppr KeyCode_RIGHT = fromText "RIGHT"
+ ppr KeyCode_ALT = fromText "ALT"
+ ppr KeyCode_CONTROL = fromText "CONTROL"
+ ppr KeyCode_SHIFT = fromText "SHIFT"
+ ppr KeyCode_BACKSPACE = fromText "BACKSPACE"
+ ppr KeyCode_TAB = fromText "TAB"
+ ppr KeyCode_ENTER = fromText "ENTER"
+ ppr KeyCode_RETURN = fromText "RETURN"
+ ppr KeyCode_ESC = fromText "ESC"
+ ppr KeyCode_DELETE = fromText "DELETE"
+
 -- CODE
 
 -- | A piece of Processing code.
@@ -612,7 +695,27 @@
 
 ----- CLASSES
 
--- | Class of Processing value types.
+-- | Class of Processing value types (@Proc_*@ types).
+--
+--   @Proc_*@ types are types from the world of Processing.
+--   Some of them are similar to Haskell types, like 'Proc_Bool'
+--   and 'Bool'. However, they are not equal. @Proc_*@ types
+--   are instance of 'Eq'. However, you should instead use methods from
+--   analog 'Proc_Eq' class. @Proc_*@ types contain expressions instead
+--   of values. Think of @2+2@ instead of @4@. Under this situation,
+--   @2+2 /= 3+1@, since they are different expressions, even if they
+--   evaluate to the same value. Actually, you will get 'True'
+--   from the evaluation of @2+2 == 3+1@, since the library is smart
+--   enough to figure out they are the same value. But, please, don't
+--   rely on this. Use the 'Proc_Eq' and 'Proc_Ord' classes instead.
+--   They return Processing boolean expressions instead of 'Bool' values.
+--   Anyway, the types of the library will try to force you to use @Proc_*@
+--   types everywhere.
+--
+--   The reason this library stores expressions instead of values is that
+--   it needs to handle things like @2+x@, where @x@ is an unknown value.
+--   However, an effort is done to ensure that each expression is reduced
+--   to its minimum extension.
 class ProcType a where
  -- | Create a variable assignment, provided
  --   the name of the variable and the value to asign.
@@ -621,36 +724,44 @@
  proc_arg :: a -> ProcArg
  -- | Variable reading.
  proc_read :: Var a -> a
+ -- | Conditional value.
+ proc_cond :: Proc_Bool -> a -> a -> a
 
 instance ProcType Proc_Bool where
  proc_asign = BoolAsign
  proc_arg = BoolArg
  proc_read (Var v) = Bool_Var v
+ proc_cond = Bool_Cond
 
 instance ProcType Proc_Int where
  proc_asign = IntAsign
  proc_arg = IntArg
  proc_read (Var v) = Int_Var v
+ proc_cond = Int_Cond
 
 instance ProcType Proc_Float where
  proc_asign = FloatAsign
  proc_arg = FloatArg
  proc_read (Var v) = Float_Var v
+ proc_cond = Float_Cond
 
 instance ProcType Proc_Image where
  proc_asign = ImageAsign
  proc_arg = ImageArg
  proc_read (Var v) = Image_Var v
+ proc_cond = Image_Cond
 
 instance ProcType Proc_Char where
  proc_asign = CharAsign
  proc_arg = CharArg
  proc_read (Var v) = Char_Var v
+ proc_cond = Char_Cond
 
 instance ProcType Proc_Text where
  proc_asign =  TextAsign
  proc_arg = TextArg
  proc_read (Var v) = Text_Var v
+ proc_cond = Text_Cond
 
 infix 4 #==, #/=
 
@@ -681,6 +792,12 @@
 instance Proc_Eq Proc_Text where
  (#==) = Text_Eq
 
+instance Proc_Eq Proc_Key where
+ (#==) = Key_Eq
+
+instance Proc_Eq Proc_KeyCode where
+ (#==) = KeyCode_Eq
+
 infix 4 #<=, #<, #>=, #>
 
 -- | 'Ord' class for @Proc_*@ values.
@@ -809,6 +926,7 @@
  , proc_draw  :: Maybe (ProcCode Draw)
  , proc_mouseClicked :: Maybe (ProcCode MouseClicked)
  , proc_mouseReleased :: Maybe (ProcCode MouseReleased)
+ , proc_keyPressed :: Maybe (ProcCode KeyPressed)
    }
 
 -- | Empty script.
@@ -819,6 +937,7 @@
  , proc_draw = Nothing
  , proc_mouseClicked = Nothing
  , proc_mouseReleased = Nothing
+ , proc_keyPressed = Nothing
    }
 
 pvoid :: Pretty a => Text -> Maybe a -> Doc
@@ -834,4 +953,5 @@
    , pvoid "draw" $ proc_draw ps
    , pvoid "mouseClicked" $ proc_mouseClicked ps
    , pvoid "mouseReleased" $ proc_mouseReleased ps
+   , pvoid "keyPressed" $ proc_keyPressed ps
      ]
diff --git a/Graphics/Web/Processing/Core/Types.hs b/Graphics/Web/Processing/Core/Types.hs
--- a/Graphics/Web/Processing/Core/Types.hs
+++ b/Graphics/Web/Processing/Core/Types.hs
@@ -15,7 +15,8 @@
   , Draw (..)
   , MouseClicked (..)
   , MouseReleased (..)
-  -- * Processing types
+  , KeyPressed (..)
+  -- * @Proc_*@ types
   , ProcType
   -- ** Bool
   , Proc_Bool, true, false
@@ -40,6 +41,8 @@
   -- * Processing classes
   , Proc_Eq (..)
   , Proc_Ord (..)
+  -- * Conditional values
+  , if_
   ) where
 
 import Graphics.Web.Processing.Core.Primal
@@ -58,3 +61,7 @@
 --   write it directly in a file.
 renderFile :: FilePath -> ProcScript -> IO ()
 renderFile fp = T.writeFile fp . renderScript
+
+-- | Conditional value.
+if_ :: ProcType a => Proc_Bool -> a -> a -> a
+if_ = proc_cond
diff --git a/Graphics/Web/Processing/Mid.hs b/Graphics/Web/Processing/Mid.hs
--- a/Graphics/Web/Processing/Mid.hs
+++ b/Graphics/Web/Processing/Mid.hs
@@ -122,8 +122,10 @@
  assignM = addCode . assignM
  writeComment = addCode . writeComment
  iff b (EventM e1) (EventM e2) = do
-   let s1 = execState e1 emptyEventState
-       s2 = execState e2 emptyEventState
+   n0 <- liftProc getVarNumber
+   let s1 = execState e1 $ emptyEventState { event_code = setVarNumber n0 }
+       n1 = fst $ runProcMWith n0 $ event_code s1 >> getVarNumber
+       s2 = execState e2 $ EventState { event_preamble = return () , event_code = setVarNumber n1 }
    addPCode $ event_preamble s1
    addPCode $ event_preamble s2
    addCode $ iff b (event_code s1) (event_code s2)
@@ -137,10 +139,11 @@
     , script_draw :: Maybe (ProcM Draw ())
     , script_mouseClicked :: Maybe (ProcM MouseClicked ())
     , script_mouseReleased :: Maybe (ProcM MouseReleased ())
+    , script_keyPressed :: Maybe (ProcM KeyPressed ())
       }
 
 emptyScriptState :: ScriptState c
-emptyScriptState = ScriptState (return ()) Nothing Nothing Nothing Nothing
+emptyScriptState = ScriptState (return ()) Nothing Nothing Nothing Nothing Nothing
 
 -- | Scripter monad. This monad is where Processing code is written.
 --   Because of some implementation details, 'ScriptM' has a context @c@.
@@ -178,6 +181,7 @@
                      (f script_draw)
                      (f script_mouseClicked)
                      (f script_mouseReleased)
+                     (f script_keyPressed)
 
 -- | Context of an event. The context determines which functions can be used.
 --   'Preamble' is not an instance of 'Context' to avoid using 'Preamble' as
@@ -197,6 +201,9 @@
 instance Context MouseReleased where
  addEvent _ c s = s { script_mouseReleased = Just c }
 
+instance Context KeyPressed where
+ addEvent _ c s = s { script_keyPressed = Just c }
+
 -- | Set an event. Different events are specified by the instances of the
 --   'Context' class.
 --
@@ -226,6 +233,7 @@
     , proc_draw = fmap execProcM $ script_draw s
     , proc_mouseClicked = fmap execProcM $ script_mouseClicked s
     , proc_mouseReleased = fmap execProcM $ script_mouseReleased s
+    , proc_keyPressed = fmap execProcM $ script_keyPressed s
       }
 
 -- Variables
diff --git a/Graphics/Web/Processing/Optimize.hs b/Graphics/Web/Processing/Optimize.hs
--- a/Graphics/Web/Processing/Optimize.hs
+++ b/Graphics/Web/Processing/Optimize.hs
@@ -21,6 +21,18 @@
 import Control.Applicative ((<$>))
 import Control.Arrow (second)
 
+boolops :: Proc_Bool -> Int
+boolops (Proc_Neg x) = 1 + boolops x
+boolops (Proc_Or x y) = 1 + boolops x + boolops y
+boolops (Proc_And x y) = 1 + boolops x + boolops y
+boolops (Float_Eq x y) = 1 + numOps x + numOps y
+boolops (Float_NEq x y) = 1 + numOps x + numOps y
+boolops (Float_LE x y) = 1 + numOps x + numOps y
+boolops (Float_L x y) = 1 + numOps x + numOps y
+boolops (Float_GE x y) = 1 + numOps x + numOps y
+boolops (Float_G x y) = 1 + numOps x + numOps y
+boolops _ = 0
+
 -- | Number of operations needed to calculate the
 --   value of a given 'Proc_Float' value.
 numOps :: Proc_Float -> Int
@@ -43,6 +55,7 @@
 numOps (Float_Arctangent x) = 1 + numOps x
 numOps (Float_Floor x) = 1 + numOps x
 numOps (Float_Noise x y) = 1 + numOps x + numOps y
+numOps (Float_Cond b x y) = boolops b + max (numOps x) (numOps y)
 
 -----------------------------------------------------
 -----------------------------------------------------
@@ -100,6 +113,7 @@
 browseFloat f@(Float_Arctangent x) = addFloat f >> browseFloat x
 browseFloat f@(Float_Floor x) = addFloat f >> browseFloat x
 browseFloat f@(Float_Noise x y) = addFloat f >> browseFloat x >> browseFloat y
+browseFloat f@(Float_Cond _ x y) = addFloat f >> browseFloat x >> browseFloat y
 browseFloat _ = return ()
 
 execCounter :: FloatCounter a -> FloatSet
@@ -266,17 +280,20 @@
               _draw
               _mouseClicked
               _mouseReleased
+              _keyPressed
                )
   = let (n1,_setup')         = subsOptimize 1 _setup
         (n2,_draw')          = maybe (n1,Nothing) (second Just . subsOptimize n1) _draw
         (n3,_mouseClicked')  = maybe (n2,Nothing) (second Just . subsOptimize n2) _mouseClicked
         (n4,_mouseReleased') = maybe (n3,Nothing) (second Just . subsOptimize n3) _mouseReleased
-        vs = fmap (\n -> CreateVar $ FloatAsign (optVarName n) 0) [1 .. n4 - 1]
+        (n5,_keyPressed')    = maybe (n4,Nothing) (second Just . subsOptimize n4) _keyPressed
+        vs = fmap (\n -> CreateVar $ FloatAsign (optVarName n) 0) [1 .. n5 - 1]
     in ProcScript (_preamble <> subsComment (mconcat vs))
                    _setup'
                    _draw'
                    _mouseClicked'
                    _mouseReleased'
+                   _keyPressed'
 
 subsComment :: ProcCode Preamble -> ProcCode Preamble
 subsComment c =
diff --git a/Graphics/Web/Processing/Simple.hs b/Graphics/Web/Processing/Simple.hs
--- a/Graphics/Web/Processing/Simple.hs
+++ b/Graphics/Web/Processing/Simple.hs
@@ -60,6 +60,12 @@
    , animateFigure
      -- ** Interactive
    , interactiveFigure
+     -- *** Keyboard
+   , Key (..)
+   , ArrowKey (..)
+   , KeyModifier (..)
+   , SpecialKey (..)
+     -- *** Custom values
      -- | Module re-export for convenience.
    , module Graphics.Web.Processing.Mid.CustomVar
    ) where
@@ -255,15 +261,20 @@
                           --   It is passed the number of frames from the
                           --   beginning.
   -> (Proc_Point -> w -> w) -- ^ Function called each time the mouse is clicked.
+  -> [(Key,w -> w)] -- ^ Key events. List of pairs, where the first component is
+                    --   a 'Key' and the second component is the reaction to that
+                    --   'Key'.
   -> ProcScript
-interactiveFigure mw mh framerate s0 _print bg step onclick = execScriptM $ do
+interactiveFigure mw mh framerate s0 _print bg step onclick keyevents = execScriptM $ do
   let w = maybe screenWidth  fromInt mw
       h = maybe screenHeight fromInt mh
   v <- newVarC s0
+  keyv <- newVar true
   on Setup $ do
      setFrameRate $ fromInt framerate
   on Draw $ do
      size w h
+     translate (intToFloat w/2) (intToFloat h/2)
      writeComment "Read state"
      s <- readVarC v
      writeComment "Background color"
@@ -279,3 +290,13 @@
      writeComment "Mouse event"
      p <- getMousePoint
      writeVarC v $ onclick p s
+  on KeyPressed $ mapM_ (keyEvent v keyv) keyevents
+
+keyEvent :: CustomValue w
+         => CustomVar w -> Var Proc_Bool -> (Key,w -> w) -> EventM KeyPressed ()
+keyEvent v keyv (k,f) = do
+  matchKey keyv k
+  b <- readVar keyv
+  iff b (readVarC v >>= writeVarC v . f)
+        (return ())
+  writeVar keyv true
diff --git a/examples/keys.hs b/examples/keys.hs
new file mode 100644
--- /dev/null
+++ b/examples/keys.hs
@@ -0,0 +1,77 @@
+
+{- Keyboard interaction demo
+
+One of the squares in a 3x3 matrix of squares
+is black and the rest is white. Use WASD keys
+to change the position of the black square.
+
+-}
+
+import Graphics.Web.Processing.Simple
+import Graphics.Web.Processing.Html
+
+main :: IO ()
+main = writeHtml "processing.js" "keydemo.pde" "Keyboard demo" "keydemo.html" theScript
+
+---------------
+-- 0 | 1 | 2 --
+-- 3 | 4 | 5 --
+-- 6 | 7 | 8 --
+---------------
+
+-- | State indicates the current position.
+type State = Proc_Int
+
+theScript :: ProcScript
+theScript =
+  interactiveFigure
+    Nothing
+    Nothing
+    30
+    4
+    cubes
+    (const $ Color 255 255 255 255)
+    (const id)
+    (const id)
+    keyEvents
+
+cubew :: Proc_Float
+cubew = 40
+
+cubew2 :: Proc_Float
+cubew2 = cubew/2
+
+corner :: Proc_Point
+corner = let w = cubew + cubew2
+         in  (negate w,w)
+
+-- | Addition of points.
+(<+>) :: Proc_Point -> Proc_Point -> Proc_Point
+(a,b) <+> (c,d) = (a+c,b+d)
+
+cubeUnit :: Proc_Bool -> Proc_Int -> Figure
+cubeUnit b n = 
+ let q = if_ b 0 255
+     c = Color q q q 255
+     (d,m) = divMod n 3
+     p = corner <+> (cubew * intToFloat m, negate $ cubew * intToFloat d)
+ in  FillColor c $ Rectangle p cubew cubew
+
+cubes :: State -> Figure
+cubes n = mconcat $ fmap (\i -> cubeUnit (n #== i) i) [0 .. 8]
+
+keyEvents :: [(Key,State -> State)]
+keyEvents = [
+   ( CharKey 'w'
+   , (\n -> if_ (n #< 3) n (n - 3))
+     )
+ , ( CharKey 'a'
+   , (\n -> if_ (mod n 3 #== 0) n (n - 1))
+     )
+ , ( CharKey 's'
+   , (\n -> if_ (n #> 5) n (n + 3))
+     )
+ , ( CharKey 'd'
+   , (\n -> if_ (mod n 3 #== 2) n (n + 1))
+     )
+ ]
diff --git a/processing.cabal b/processing.cabal
--- a/processing.cabal
+++ b/processing.cabal
@@ -1,5 +1,5 @@
 Name: processing
-Version: 1.0.0.1
+Version: 1.0.1.0
 Author: Daniel Díaz
 Category: Graphics
 Build-type: Simple
@@ -56,6 +56,7 @@
   readme.md
   examples/twist.hs
   examples/mill.hs
+  examples/keys.hs
 
 Source-repository head
   type: git