Add undo button to practice.

www/js/game.js

@@ -526,7 +526,7 @@ GAME.Game = class {
                                 }
 
                                 if(pieces_blocking == 1 && stride > 0) {
-                                    // Apply blocking to last .
+                                    // Apply blocking to last piece tile.
                                     for(let idist = 1; idist < dist; idist++) {
                                         if(this.board.tiles[tiles[tiles.length - idist].tile].piece !== null) {
                                             tiles[tiles.length - idist].block = dir_mask;

www/js/interface.js

@@ -1005,6 +1005,15 @@ const INTERFACE = {
         INTERFACE.replay_jump(INTERFACE_DATA.history.length, false);
     },
 
+    undo() {
+        INTERFACE_DATA.auto_mode = null;
+        if(INTERFACE_DATA.history.length > 0) {
+            GAME.init();
+            INTERFACE_DATA.history.pop();
+            INTERFACE.replay_jump(INTERFACE_DATA.history.length, false);
+        }
+    },
+
     message(code, data) {
         if(data === null) { return; }
 

www/js/language.js

@@ -47,6 +47,7 @@ LANGUAGE.Terms = {
     back: new LANGUAGE.Term( "Back", "戻る" ),
     resign: new LANGUAGE.Term( "Resign", "投了" ),
     confirm: new LANGUAGE.Term( "Confirm", "確認" ),
+    undo: new LANGUAGE.Term( "Undo", "待った" ),
     reset: new LANGUAGE.Term( "Reset", "リセット" ),
     auto: new LANGUAGE.Term( "Auto", "自動" ),
 

www/js/scene.js

@@ -642,6 +642,7 @@ const SCENES = {
         }
         load(data) {
             let buttons_bottom = [ ];
+            buttons_bottom.push(UI.button(LANG("undo"), () => { INTERFACE.undo(); }));
             buttons_bottom.push(UI.button(LANG("reset"), () => { INTERFACE.reset(); }));
             buttons_bottom.push(UI.button(LANG("back"), () => { LOAD(SCENES.Browse); }));