Added some constrant definitions

src/app.rs

@@ -0,0 +1,13 @@
+
+use piston::*;
+
+pub struct App;
+
+impl App {
+    pub fn new() -> App {
+        App
+    }
+}
+
+impl Game for App {
+}

src/main.rs

@@ -0,0 +1,33 @@
+
+#![feature(globs)]
+
+extern crate rand;
+
+extern crate graphics;
+extern crate piston;
+
+use piston::*;
+
+mod app;
+mod settings;
+
+type GameWindowBackEnd = GameWindowSDL2;
+
+fn main() {
+    let mut game_window: GameWindowBackEnd = GameWindow::new(
+        GameWindowSettings::new (
+            "Rust-2048".to_owned(),
+            settings::WINDOW_SIZE,
+            false,
+            true,
+            settings::WINDOW_BACKGROUND_COLOR,
+        )
+    );
+
+    let mut asset_store = AssetStore::from_folder(settings::ASSET_FOLDER);
+
+    let mut app = app::App::new();
+
+    app.run(&mut game_window, &mut asset_store);
+}
+

src/settings.rs

@@ -0,0 +1,35 @@
+
+pub static ASSET_FOLDER: &'static str = "assets";
+
+pub static WINDOW_SIZE: [u32, ..2] = [400, 400];
+pub static WINDOW_BACKGROUND_COLOR: [f32, ..4] = [250.0 / 255.0, 248.0 / 255.0, 239.0 / 255.0, 1.0];
+pub static WINDOW_PADDING: f64 = 12.0;
+
+pub static TILE_SIZE: [f64, ..2] = [72.0, 72.0];
+pub static TILE_PADDING: f64 = 12.0;
+pub static TILE_BACKGROUND_COLOR: [f32, ..4] = [187.0 / 255.0, 173.0 / 255.0, 160.0 / 255.0, 1.0];
+pub static TILES_COLOR: [[f32, ..4], ..12] = [
+    /// empty color
+    [204.0 / 255.0, 192.0 / 255.0, 179.0 / 255.0, 1.0],
+    /// 2 color
+    [238.0 / 255.0, 228.0 / 255.0, 218.0 / 255.0, 1.0],
+    /// 4 color
+    [237.0 / 255.0, 224.0 / 255.0, 200.0 / 255.0, 1.0],
+    /// 8 color
+    [242.0 / 255.0, 177.0 / 255.0, 121.0 / 255.0, 1.0],
+    /// 16 color
+    [245.0 / 255.0, 149.0 / 255.0, 99.0 / 255.0, 1.0],
+    /// 32 color
+    [246.0 / 255.0, 124.0 / 255.0, 95.0 / 255.0, 1.0],
+    /// 64 color
+    [246.0 / 255.0, 94.0 / 255.0, 59.0 / 255.0, 1.0],
+    /// 128 color
+    [237.0 / 255.0, 207.0 / 255.0, 114.0 / 255.0, 1.0],
+    /// 256 color
+    [237.0 / 255.0, 204.0 / 255.0, 97.0 / 255.0, 1.0],
+    /// 512 color
+    [237.0 / 255.0, 200.0 / 255.0, 80.0 / 255.0, 1.0],
+]
+
+pub static LABEL_COLOR: [f32, ..4] = [187.0 / 255.0, 173.0 / 255.0, 160.0 / 255.0, 1.0];
+pub static BUTTON_COLOR: [f32, ..4] = [142.0 / 255.0, 122.0 / 255.0, 102.0 / 255.0, 1.0];