diff --git a/src/host/labyrinth/Board.java b/src/host/labyrinth/Board.java
index 0702a00..4f08c9f 100644
--- a/src/host/labyrinth/Board.java
+++ b/src/host/labyrinth/Board.java
@@ -42,6 +42,7 @@ class Board {
     */
    Board(int N, int S) {
       assert (N%2 != 0) : "Board's size has to be an odd number.";
+      assert (S <= (N*N-2)) : "At least 2 tiles has to be without supplies.";
       this.N   = Session.boardSize = N;
       this.S   = S;
       this.W   = 0;
@@ -394,7 +395,7 @@ class Board {
       if (tiles[tileId].hasWalls() >= Const.maxTileWalls)
          return false;
       Range dirs = new Range(DirRange.Begin, DirRange.End, DirRange.Step);
-      for (int dir ; (dir = dirs.get()) != Const.noTileId ; )
+      for (int dir = dirs.get() ; dir != Const.EOR ; dir = dirs.get())
          if (isWallableDir(tileId, dir))
             return true;
       return false;
@@ -457,7 +458,7 @@ class Board {
       for (int tileId, i =0, walls =0, shuffleMark =0 ; true ; ) {
          // randomly pick a wallable tile.
          do {
-            if ((tileId = randTiles.get())== Const.noTileId) {
+            if ((tileId = randTiles.get())== Const.EOR) {
                if (i == shuffleMark)   // Wallable tiles exhausted.
                   return walls;
                else {                  // Re-shuffle and continue.
diff --git a/src/host/labyrinth/Common.java b/src/host/labyrinth/Common.java
index 5b71c2e..5f2022e 100644
--- a/src/host/labyrinth/Common.java
+++ b/src/host/labyrinth/Common.java
@@ -18,6 +18,7 @@ class Const {
    static final int maxTileWalls = 2;  /**< Number of maximum walls for each tile on the board */
    static final int noSupply =-1;      /**< Number to indicate the absent of supply */
    static final int noTileId =-1;      /**< Number to indicate wrong tileId */
+   static final int EOR =-1;           /**< Number to indicate the End Of Range */
 }
 /**
  * Application wide object to hold settings like values for the session.
diff --git a/src/host/labyrinth/Game.java b/src/host/labyrinth/Game.java
index 3910ac5..db7a0d3 100644
--- a/src/host/labyrinth/Game.java
+++ b/src/host/labyrinth/Game.java
@@ -80,7 +80,7 @@ public class Game {
                break;
 
             case "-s":
-            case "--suplies":
+            case "--supplies":
                if (i+1 < args.length)
                   Session.supplySize = Integer.parseInt(args[++i]);
                break;