diff --git a/src/main.rs b/src/main.rs
index fb45b67..25cba57 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -11,6 +11,7 @@ use piston::*;
 mod app;
 mod board;
 mod settings;
+mod tile;
 
 type GameWindowBackEnd = GameWindowSDL2;
 
diff --git a/src/settings.rs b/src/settings.rs
index 5418579..1aa009e 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -41,6 +41,7 @@ pub static TILES_COLOR: [[f32, ..4], ..10] = [
     // 512 color
     [237.0 / 255.0, 200.0 / 255.0, 80.0 / 255.0, 1.0],
 ];
+pub static TILE_UNKNOW_COLOR: [f32, ..4] = [0.8, 0.0, 0.0, 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];