1 files changed, 6 insertions, 4 deletions

diff --git a/rules.js b/rules.js
index a5b0bd1..85c8cc2 100644
--- a/rules.js
+++ b/rules.js
@@ -258,7 +258,7 @@ function clear_undo() {
 
 function push_undo() {
 	game.undo.push(JSON.stringify(game, (k,v) => {
-		if (k === 'undo') return undefined;
+		if (k === 'undo') return 0;
 		if (k === 'log') return v.length;
 		return v;
 	}));
@@ -267,7 +267,7 @@ function push_undo() {
 function pop_undo() {
 	let save_undo = game.undo;
 	let save_log = game.log;
-	Object.assign(game, JSON.parse(save_undo.pop()));
+	game = JSON.parse(save_undo.pop());
 	game.undo = save_undo;
 	save_log.length = game.log;
 	game.log = save_log;
@@ -3362,7 +3362,7 @@ exports.action = function (state, current, action, arg) {
 		S[action](arg, current);
 	else
 		throw new Error("Invalid action: " + action);
-	return state;
+	return game;
 }
 
 exports.resign = function (state, current) {
@@ -3378,9 +3378,11 @@ exports.resign = function (state, current) {
 		else
 			game.result = PERSIA;
 	}
-	return state;
+	return game;
 }
 
+exports.checkpoints = [ "campaign" ];
+
 exports.view = function(state, current) {
 	game = state;