diff --git a/.eslintrc.js b/.eslintrc.js
index 322d2d441..b3c9701e0 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -28,8 +28,6 @@ module.exports = {
 		'SquireUI': "readonly",
 		// node_modules/knockout but dev/External/ko.js is used
 //		'ko': "readonly",
-		// node_modules/simplestatemanager
-		'ssm': "readonly",
 		// vendors/routes/
 		'hasher': "readonly",
 		'signals': "readonly",
diff --git a/dev/App/Abstract.js b/dev/App/Abstract.js
index 4453a7f89..9428f7a19 100644
--- a/dev/App/Abstract.js
+++ b/dev/App/Abstract.js
@@ -110,43 +110,10 @@ class AbstractApp {
 		initOnStartOrLangChange(initNotificationLanguage);
 
 		if (!mobile) {
-			$htmlCL.add('rl-desktop');
-
-			ssm.addState({
-				id: 'mobile',
-				query: '(max-width: 767px)',
-				onEnter: () => {
-					$htmlCL.add('ssm-state-mobile');
-					leftPanelDisabled(true);
-				},
-				onLeave: () => {
-					$htmlCL.remove('ssm-state-mobile');
-					leftPanelDisabled(false);
-				}
-			});
-
-			ssm.addState({
-				id: 'tablet',
-				query: '(min-width: 768px) and (max-width: 999px)',
-				onEnter: () => $htmlCL.add('ssm-state-tablet'),
-				onLeave: () => $htmlCL.remove('ssm-state-tablet')
-			});
-
-			ssm.addState({
-				id: 'desktop',
-				query: '(min-width: 1000px) and (max-width: 1400px)',
-				onEnter: () => $htmlCL.add('ssm-state-desktop'),
-				onLeave: () => $htmlCL.remove('ssm-state-desktop')
-			});
-
-			ssm.addState({
-				id: 'desktop-large',
-				query: '(min-width: 1401px)',
-				onEnter: () => $htmlCL.add('ssm-state-desktop-large'),
-				onLeave: () => $htmlCL.remove('ssm-state-desktop-large')
-			});
+			// mobile
+			window.addEventListener('resize', () => leftPanelDisabled(767 >= window.innerWidth));
 		} else {
-			$htmlCL.add('ssm-state-mobile', 'rl-mobile');
+			$htmlCL.add('rl-mobile');
 			leftPanelDisabled(true);
 		}
 
diff --git a/dev/Styles/Layout.less b/dev/Styles/Layout.less
index 3a859be8e..68f4487fa 100644
--- a/dev/Styles/Layout.less
+++ b/dev/Styles/Layout.less
@@ -188,8 +188,8 @@ html:not(.rl-left-panel-disabled) #rl-left.resizable > .resizer,
 //	-webkit-overflow-scrolling: touch;
 }
 
-html.ssm-state-desktop-large {
-
+/* desktop-large */
+@media screen and (min-width: 1401px) {
 	#rl-left {
 		width: @rlLeftWidth + 20;
 	}
@@ -211,8 +211,8 @@ html.ssm-state-desktop-large {
 	}
 }
 
-html.ssm-state-desktop {
-
+/* desktop */
+@media screen and (min-width: 1000px) and (max-width: 1400px) {
 	#rl-left {
 		width: @rlLeftWidth;
 	}
@@ -234,8 +234,8 @@ html.ssm-state-desktop {
 	}
 }
 
-html.ssm-state-tablet, html.ssm-state-mobile {
-
+/* mobile and tablet */
+@media screen and (max-width: 999px) {
 	#rl-left {
 		width: 155px;
 	}
@@ -267,8 +267,8 @@ html.ssm-state-tablet, html.ssm-state-mobile {
 	}
 }
 
-html.ssm-state-tablet {
-
+/* tablet */
+@media screen and (min-width: 768px) and (max-width: 999px) {
 	.b-contacts-content.modal {
 		width: 800px;
 	}
diff --git a/dev/Styles/MessageList.less b/dev/Styles/MessageList.less
index a8438c505..4f8d97452 100644
--- a/dev/Styles/MessageList.less
+++ b/dev/Styles/MessageList.less
@@ -608,7 +608,8 @@ html.rl-no-preview-pane {
 	}
 }
 
-html.ssm-state-desktop-large {
+/* desktop-large */
+@media screen and (min-width: 1401px) {
 	.messageList .b-content .messageListItem {
 		font-size: 13px;
 		.dateParent {
diff --git a/dev/Styles/MessageView.less b/dev/Styles/MessageView.less
index 412da9219..ea2cebdb0 100644
--- a/dev/Styles/MessageView.less
+++ b/dev/Styles/MessageView.less
@@ -651,7 +651,7 @@ html .messageItem {
 	}
 }
 
-html.rl-desktop .messageItem {
+html:not(.rl-mobile) .messageItem {
 	.buttonUp, .buttonFull {
 		display: none !important;
 	}
diff --git a/dev/Styles/SystemDropDown.less b/dev/Styles/SystemDropDown.less
index 870ddc6c8..360b70897 100644
--- a/dev/Styles/SystemDropDown.less
+++ b/dev/Styles/SystemDropDown.less
@@ -129,8 +129,11 @@
 	}
 }
 
-html.ssm-state-mobile .accountPlace {
-	max-width: 150px !important;
+/* mobile */
+@media screen and (max-width: 767px) {
+	.accountPlace {
+		max-width: 150px !important;
+	}
 }
 
 @keyframes firstBar {
diff --git a/package.json b/package.json
index 2e39fd3ac..9c1566495 100644
--- a/package.json
+++ b/package.json
@@ -91,7 +91,6 @@
     "prettier": "1.19.1",
     "raw-loader": "4.0.0",
     "rimraf": "3.0.2",
-    "simplestatemanager": "4.1.1",
     "style-loader": "1.1.3"
   },
   "dependencies": {
diff --git a/tasks/config.js b/tasks/config.js
index b8b9f401c..ed8fc8e0f 100644
--- a/tasks/config.js
+++ b/tasks/config.js
@@ -89,7 +89,6 @@ config.paths.js = {
 			'vendors/bootstrap/js/bootstrap.native.min.js', // fixed
 			'vendors/knockout/build/output/knockout-latest.js',
 			'vendors/knockout-sortable/build/knockout-sortable.min.js ',
-			'node_modules/simplestatemanager/dist/ssm.min.js',
 			'vendors/lightgallery/dist/js/lightgallery.min.js', // license
 			'vendors/lightgallery/dist/js/lg-fullscreen.min.js',
 			'vendors/lightgallery/dist/js/lg-thumbnail.min.js',
diff --git a/yarn.lock b/yarn.lock
index 105c7f98b..93bbad272 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -5883,11 +5883,6 @@ signal-exit@^3.0.0, signal-exit@^3.0.2:
   resolved "https://registry.yarnpkg.com/signal-exit/-/signal-exit-3.0.3.tgz#a1410c2edd8f077b08b4e253c8eacfcaf057461c"
   integrity sha512-VUJ49FC8U1OxwZLxIbTTrDvLnf/6TDgxZcK8wxR8zs13xpx7xbG60ndBlhNrFi2EMuFRoeDoJO7wthSLq42EjA==
 
-simplestatemanager@4.1.1:
-  version "4.1.1"
-  resolved "https://registry.yarnpkg.com/simplestatemanager/-/simplestatemanager-4.1.1.tgz#723879947cd8a40dd20645a0ee6a7cadcc669d4f"
-  integrity sha512-RRhB4rPEU10dwERLLrOTx3rdKW6sLHTsYpr+SBKoh/Vl4XETgNnux45+wgX59M1cDiJQX/CuMVu0eOWFSDECDg==
-
 slash@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/slash/-/slash-1.0.0.tgz#c41f2f6c39fc16d1cd17ad4b5d896114ae470d55"