update README

Author: Javran

README.md

@@ -13,14 +13,24 @@ you can use the following command to build this project:
 
     cabal build
 
-The executable will be located at `dist/build/h2048-simple/h2048-simple`,
+The executable will be located at `dist/build/h2048-simple/h2048-vty`,
 to run the program:
 
-    ./dist/build/h2048-simple/h2048-simple
+    ./dist/build/h2048-simple/h2048-vty
 
 Or alternatively:
 
+    cabal run h2048-vty
+
+If you have trouble building the `vty` CLI version,
+you can try to turn off feature `vty` it and use `h2028-simple`:
+
+    cabal configure --flag="-vty"
+    cabal build
+    # now the program should be ready
     cabal run h2048-simple
+    # or alternatively:
+    ./dist/build/h2048-simple/h2048-simple
 
 ### Without cabal
 
@@ -30,19 +40,29 @@ First make sure the following dependencies are installed:
 * [mtl](http://hackage.haskell.org/package/mtl)
 * [MonadRandom](http://hackage.haskell.org/package/MonadRandom)
 
-You can use following commands to run this project without cabal:
+In addition, if you want to play with vty CLI version, the following dependencies
+are also required:
+
+* [text](http://hackage.haskell.org/package/text)
+* [vty](http://hackage.haskell.org/package/vty)
+* [vty-ui](http://hackage.haskell.org/package/vty-ui)
+
+You can use following commands to run the program without cabal:
 
     cd src # assume your working directory is the project home.
+    # to play the simple CLI version
     runhaskell MainSimple.hs
+    # to play the vty CLI version
+    runhaskell MainVty.hs
 
 ## How to play
 
-Run command `runhaskell h2048.hs` from your terminal.
-
 keys:
 
 * `q`: quit
 * `i`: up
 * `k`: down
 * `j`: left
 * `l`: right
+
+If you are using `h2048-vty`, you can also use arrow keys.