diff --git a/www/js/game.js b/www/js/game.js
index a08dd6d..1c35cf7 100644
--- a/www/js/game.js
+++ b/www/js/game.js
@@ -192,8 +192,8 @@ GAME.PieceMovement = class {
 
     rotate() {
         let copy = new GAME.PieceMovement();
-        copy.direction = BITWISE.rotate_blocks(this.direction);
-        copy.stride = BITWISE.rotate_blocks(this.stride);
+        copy.direction = BITWISE.rotate_blocks6(this.direction);
+        copy.stride = BITWISE.rotate_blocks12(this.stride);
         copy.alt = this.alt;
         return copy;
     }
@@ -425,7 +425,7 @@ GAME.Game = class {
         let hex = this.board.tiles[tile].hex;
 
         let directions = moves.direction;
-        let block_directions = piece.blocking | BITWISE.rotate_blocks(piece.blocking);
+        let block_directions = piece.blocking | BITWISE.rotate_blocks6(piece.blocking);
 
         // Check directions of movement.
         for(let mask = BITWISE.lsb(directions); directions > 0; mask = BITWISE.lsb(directions)) {
@@ -565,7 +565,7 @@ GAME.Game = class {
             return false;
         }
 
-        mask = BITWISE.rotate_blocks(mask);
+        mask = BITWISE.rotate_blocks6(mask);
         let moves = target.moves();
 
         // King cannot swap onto tile that is threatened.
@@ -582,7 +582,7 @@ GAME.Game = class {
 
         if(piece.promoted) {
             let hex = this.board.tiles[piece.tile].hex;
-            let block_directions = piece.blocking | BITWISE.rotate_blocks(piece.blocking);
+            let block_directions = piece.blocking | BITWISE.rotate_blocks6(piece.blocking);
 
             switch(piece.piece) {
                 case GAME.Const.PieceId.Knight: {
@@ -629,9 +629,9 @@ GAME.Game = class {
                 case GAME.Const.PieceId.Castle: {
                     let mask_back = 1 << 3;
                     if(piece.player == GAME.Const.Player.Dusk) {
-                        mask_back = BITWISE.rotate_blocks(mask_back);
+                        mask_back = BITWISE.rotate_blocks6(mask_back);
                     }
-                    let mask_column = mask_back | BITWISE.rotate_blocks(mask_back);
+                    let mask_column = mask_back | BITWISE.rotate_blocks6(mask_back);
 
                     let direction = GAME.Const.get_direction(BITWISE.ffs(mask_back));
                     let move_hex = hex.copy();
diff --git a/www/js/util.js b/www/js/util.js
index 8347236..e20492d 100644
--- a/www/js/util.js
+++ b/www/js/util.js
@@ -159,7 +159,7 @@ const BITWISE = {
         return ((mask + (mask >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
     },
 
-    rotate_blocks(mask)
+    rotate_blocks6(mask)
     {
         const r1 = 0x00003F; // first 6 bits
         const r2 = 0x000FC0; // second 6 bits
@@ -175,6 +175,20 @@ const BITWISE = {
 
         return v1 | v2 | v3;
     },
+
+    rotate_blocks12(mask)
+    {
+        const r1 = 0x00000FFF; // first 12 bits
+        const r2 = 0x00FFF000; // second 12 bits
+
+        let v1 = (r1 & mask) << 6;
+        let v2 = (r2 & mask) << 6;
+
+        v1 = (v1 & r1) | ((v1 & ~r1) >> 12);
+        v2 = (v2 & r2) | ((v2 & ~r2) >> 12);
+
+        return v1 | v2;
+    },
 };
 
 const MATH = {