diff --git a/.babelrc b/.babelrc
index 1458c7de..70c6f3a3 100644
--- a/.babelrc
+++ b/.babelrc
@@ -10,7 +10,8 @@
 								"last 2 Chrome versions"
 							]
 						},
-						"useBuiltIns": "entry"
+						"useBuiltIns": "entry",
+						"corejs": 3
 					}
 				],
 				"@babel/preset-react"
@@ -35,7 +36,8 @@
 								"iOS >= 10"
 							]
 						},
-						"useBuiltIns": "entry"
+						"useBuiltIns": "entry",
+						"corejs": 3
 					}
 				],
 				"@babel/preset-react"
@@ -56,7 +58,8 @@
 								"last 2 Chrome versions"
 							]
 						},
-						"useBuiltIns": "entry"
+						"useBuiltIns": "entry",
+						"corejs": 3
 					}
 				],
 				"@babel/preset-react"
diff --git a/lib/stage.js b/lib/stage.js
index 93d4f869..179da40b 100644
--- a/lib/stage.js
+++ b/lib/stage.js
@@ -193,12 +193,14 @@ class Stage {
 
 	renderBoardComponent() {
 		const boardComponent = React.createElement(BoardComponent, this.boardComponentProps);
-		this.boardComponent = ReactDOM.render(boardComponent, $('.board-area').get(0));
+		ReactDOM.render(boardComponent, $('.board-area').get(0));
+		this.boardComponent = boardComponent;
 	}
 
 	renderPanelComponent() {
 		const panelComponent = React.createElement(PanelComponent, this.panelComponentProps);
-		this.panelComponent = ReactDOM.render(panelComponent, $('.panel-area').get(0));
+		ReactDOM.render(panelComponent, $('.panel-area').get(0));
+		this.panelComponent = panelComponent;
 	}
 
 	saveStage() {
diff --git a/package.json b/package.json
index a40870fa..4be34ceb 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "",
   "main": "index.js",
   "engines": {
-    "node": "^11.0.0"
+    "node": "^13.0.0"
   },
   "scripts": {
     "js": "cross-env BABEL_ENV=debug webpack --mode development",
@@ -47,95 +47,95 @@
   },
   "homepage": "https://github.com/tsg-ut/mnemo#readme",
   "devDependencies": {
-    "@babel/core": "^7.0.0",
-    "@babel/plugin-proposal-class-properties": "^7.0.0",
-    "@babel/plugin-transform-async-to-generator": "^7.0.0",
-    "@babel/preset-env": "^7.0.0",
-    "@babel/preset-react": "^7.0.0",
-    "autoprefixer": "^9.1.5",
-    "babel-eslint": "^10.0.1",
-    "babel-loader": "^8.0.0",
+    "@babel/core": "^7.8.6",
+    "@babel/plugin-proposal-class-properties": "^7.8.3",
+    "@babel/plugin-transform-async-to-generator": "^7.8.3",
+    "@babel/preset-env": "^7.8.6",
+    "@babel/preset-react": "^7.8.3",
+    "autoprefixer": "^9.7.4",
+    "babel-eslint": "^10.1.0",
+    "babel-loader": "^8.0.6",
     "babel-minify-webpack-plugin": "^0.3.1",
-    "babel-plugin-istanbul": "^5.0.1",
+    "babel-plugin-istanbul": "^6.0.0",
     "babel-plugin-transform-inline-environment-variables": "^6.8.0",
-    "babel-plugin-transform-react-remove-prop-types": "^0.4.18",
+    "babel-plugin-transform-react-remove-prop-types": "^0.4.24",
     "chai": "^4.2.0",
     "chai-enzyme": "beta",
-    "chai-http": "^4.2.0",
+    "chai-http": "^4.3.0",
     "chai-things": "^0.2.0",
-    "chokidar-cli": "^1.2.1",
-    "codecov": "^3.1.0",
-    "concurrently": "^4.0.1",
+    "chokidar-cli": "^2.1.0",
+    "codecov": "^3.6.5",
+    "concurrently": "^5.1.0",
     "create-react-class": "^15.6.3",
-    "cross-env": "^5.2.0",
-    "cssnano": "^4.1.4",
-    "electron": "^4.0.0",
-    "enzyme": "^3.6.0",
-    "enzyme-adapter-react-16": "^1.5.0",
-    "eslint": "^5.6.0",
-    "eslint-plugin-react": "^7.11.1",
-    "fetch-ponyfill": "^6.0.2",
-    "file-url": "^2.0.2",
-    "github-fork-ribbon-css": "^0.2.1",
-    "gsap": "^2.0.2",
+    "cross-env": "^7.0.0",
+    "cssnano": "^4.1.10",
+    "electron": "^8.0.2",
+    "enzyme": "^3.11.0",
+    "enzyme-adapter-react-16": "^1.15.2",
+    "eslint": "^6.8.0",
+    "eslint-plugin-react": "^7.18.3",
+    "fetch-ponyfill": "^6.1.0",
+    "file-url": "^3.0.0",
+    "github-fork-ribbon-css": "^0.2.3",
+    "gsap": "^3.2.4",
     "hammerjs": "^2.0.8",
-    "immutable": "^4.0.0-rc.9",
+    "immutable": "^4.0.0-rc.12",
     "istanbul": "next",
-    "jquery": "^3.3.1",
-    "karma": "^4.0.0",
-    "karma-coverage": "^1.1.2",
-    "karma-electron": "^6.0.0",
+    "jquery": "^3.4.1",
+    "karma": "^4.4.1",
+    "karma-coverage": "^2.0.1",
+    "karma-electron": "^6.3.0",
     "karma-mocha": "^1.3.0",
     "karma-sourcemap-loader": "^0.3.7",
     "karma-spec-reporter": "^0.0.32",
-    "karma-webpack": "^3.0.5",
-    "less": "^3.8.1",
+    "karma-webpack": "^4.0.2",
+    "less": "^3.11.1",
     "livescript-loader": "^0.1.6",
-    "mathjs": "^5.1.2",
+    "mathjs": "^6.6.1",
     "microtime": "^3.0.0",
-    "mocha": "^6.0.0",
+    "mocha": "^7.1.0",
     "mocha-logger": "^1.0.6",
     "mocha-webpack": "^2.0.0-beta.0",
     "mockery": "^2.1.0",
-    "nightmare": "^3.0.1",
-    "normalize.css": "^8.0.0",
+    "nightmare": "^3.0.2",
+    "normalize.css": "^8.0.1",
     "postcss-assets": "^5.0.0",
-    "postcss-cli": "^6.0.0",
-    "postcss-flexbugs-fixes": "^4.1.0",
-    "postcss-font-magician": "^2.2.1",
-    "prop-types": "^15.6.2",
+    "postcss-cli": "^7.1.0",
+    "postcss-flexbugs-fixes": "^4.2.0",
+    "postcss-font-magician": "^2.3.1",
+    "prop-types": "^15.7.2",
     "pug-cli": "^1.0.0-alpha6",
-    "react": "^16.5.2",
-    "react-dom": "^16.5.2",
+    "react": "^16.13.0",
+    "react-dom": "^16.13.0",
     "react-gsap-enhancer": "^0.3.0",
     "react-hammerjs": "JedWatson/react-hammerjs",
-    "react-measure": "^2.1.2",
-    "react-test-renderer": "^16.5.2",
-    "sequelize-cli": "^5.0.0",
-    "sqlite3": "^4.0.2",
+    "react-measure": "^2.3.0",
+    "react-test-renderer": "^16.13.0",
+    "sequelize-cli": "^5.5.1",
+    "sqlite3": "^4.1.1",
     "svg-path-generator": "^1.1.0",
-    "umzug": "^2.1.0",
-    "webpack": "^4.20.2",
-    "webpack-cli": "^3.1.1",
-    "webpack-dev-server": "^3.1.9",
+    "umzug": "^2.2.0",
+    "webpack": "^4.42.0",
+    "webpack-cli": "^3.3.11",
+    "webpack-dev-server": "^3.10.3",
     "webpack-node-externals": "^1.7.2"
   },
   "dependencies": {
-    "bluebird": "^3.5.2",
-    "body-parser": "^1.18.3",
+    "bluebird": "^3.7.2",
+    "body-parser": "^1.19.0",
     "common-tags": "^1.8.0",
-    "core-js": "^2.5.7",
-    "cors": "^2.8.4",
-    "express": "^4.16.3",
+    "core-js": "^3.6.4",
+    "cors": "^2.8.5",
+    "express": "^4.17.1",
     "express-promise-router": "^3.0.3",
-    "forcedomain": "^1.0.0",
+    "forcedomain": "^2.0.0",
     "lcov-result-merger": "^3.1.0",
     "node-slack": "^0.0.7",
-    "pg": "^6.4.2",
-    "regenerator-runtime": "^0.12.1",
-    "request": "^2.88.0",
-    "seedrandom": "^2.4.4",
-    "sequelize": "^4.39.0"
+    "pg": "^7.18.2",
+    "regenerator-runtime": "^0.13.3",
+    "request": "^2.88.2",
+    "seedrandom": "^3.0.5",
+    "sequelize": "^5.21.5"
   },
   "resolutions": {
     "webpack-sources": "1.0.1"
diff --git a/test/unit/stages.ls b/test/unit/stages.ls
index 36e6158b..011d930e 100644
--- a/test/unit/stages.ls
+++ b/test/unit/stages.ls
@@ -91,8 +91,9 @@ factorization-calc = (n) ->
 spaceship-calc = (a, b) -> Math.sign a - b
 
 ten-thousandth-digit-calc = (n) ->
-  mathjs.config precision: 20000
-  x = mathjs.divide mathjs.bignumber(1), mathjs.bignumber(n)
+  m = mathjs.create mathjs.all
+  m.config precision: 10010
+  x = m.divide m.bignumber(1), m.bignumber(n)
   return x.to-string!split '.' .1.9999 |> parse-int
 
 eight-eight-zero-nine-calc = (n) ->
@@ -371,6 +372,7 @@ describe 'Stage Data' ->
 
   describe '10000th-digit stage' ->
     It 'generates 10000th-digit' ->
+      @timeout 30000
       test-many-times-with-random (random) ->
         io = ten-thousandth-digit.io-generator random