diff --git a/.vscode/settings.json b/.vscode/settings.json
index 1474f5d..020e13a 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -25,5 +25,19 @@
   "workbench.statusBar.feedback.visible": false,
   "xo.format.enable": true,
   "xo.enable": true,
-  "gitlens.views.repositories.files.layout": "list"
+  "gitlens.views.repositories.files.layout": "list",
+  "cSpell.words": [
+    "atcoder",
+    "betalib",
+    "brainfuck",
+    "caml",
+    "clar",
+    "commonlib",
+    "drafear",
+    "dropdown",
+    "glyphicon",
+    "o",
+    "oninstall",
+    "unlambda"
+  ]
 }
diff --git a/package.json b/package.json
index 1571a13..123a633 100644
--- a/package.json
+++ b/package.json
@@ -3,13 +3,13 @@
   "description": "Comfort your atcoder life. For more detail, visit https://github.com/drafear/comfortable-atcoder",
   "scripts": {
     "build": "run-s build:*",
-    "build:xo": "xo src/**/*.ts",
     "build:init": "rm -rf dist",
     "build:cp": "cp -r src dist && rm -rf dist/**/*.less",
+    "build:css": "less-watch-compiler --run-once src dist",
     "build:ts": "parcel build --target node src/**/*.ts",
     "start": "npm run watch",
     "watch": "run-p watch:*",
-    "watch:less": "less-watch-compiler src src",
+    "watch:less": "less-watch-compiler src dist",
     "watch:build": "parcel --target node src/**/*.ts",
     "watch:test": "jest --watch",
     "package": "npm run build && zip -rq Release.zip dist"
@@ -101,6 +101,7 @@
         }
       ],
       "typescript/explicit-function-return-type": 0,
+      "no-useless-constructor": 0,
       "no-alert": 0,
       "no-negated-condition": 0,
       "capitalized-comments": 0,
diff --git a/src/content/add-tweet-button.ts b/src/content/add-tweet-button.ts
new file mode 100644
index 0000000..a852576
--- /dev/null
+++ b/src/content/add-tweet-button.ts
@@ -0,0 +1,80 @@
+import * as Commonlib from './all';
+import * as Betalib from './betalib';
+
+Commonlib.runIfEnableAndLoad('add-tweet-button', async () => {
+  const isMyPage = $('#user-nav-tabs .glyphicon-cog').length >= 1;
+  if (!isMyPage) {
+    return;
+  }
+
+  const isDetailPage = /^\/users\/[^/]+\/history\/?$/.test(location.pathname);
+  const userId = (location.pathname.match(/^\/users\/([^/]+)/) as string[])[1];
+
+  async function getTable(): Promise<JQuery<HTMLElement>> {
+    // if (isDetailPage) {
+    //   return $('#history');
+    // }
+    // else {
+    const html = await (await fetch(`/users/${userId}/history`)).text();
+    return $(html).find('#history');
+    // }
+  }
+
+  function getLatestContestResult(contestResults: Betalib.ContestResult[]): Betalib.ContestResult | null {
+    if (contestResults.length === 0) {
+      return null;
+    }
+    let res = contestResults[0];
+    for (const result of contestResults) {
+      if (result.date > res.date) {
+        res = result;
+      }
+    }
+    return res;
+  }
+
+  function makeTweetText(contestResult: Betalib.ContestResult, isHighest = false): string {
+    const r = contestResult;
+    if (r instanceof Betalib.RatedContestResult) {
+      const highestStr = isHighest ? ', Highest!!' : '';
+      return `I took ${r.getRankStr()} place in ${r.contestName}\n\nRating: ${r.newRating - r.diff} -> ${r.newRating} (${r.getDiffStr()}${highestStr})\nPerformance: ${r.performance}\n#${r.contestId}`;
+    }
+    else {
+      return `I took ${r.getRankStr()} place in ${r.contestName}\n#${r.contestId}`;
+    }
+  }
+
+  function isHighest(targetContestResult: Betalib.ContestResult, contestResults: Betalib.ContestResult[]) {
+    if (!(targetContestResult instanceof Betalib.RatedContestResult)) {
+      return false;
+    }
+    for (const result of contestResults) {
+      if (result.contestId === targetContestResult.contestId) {
+        continue;
+      }
+      if (!(result instanceof Betalib.RatedContestResult)) {
+        continue;
+      }
+      if (result.newRating >= targetContestResult.newRating) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  const $table = await getTable();
+  const contestResults = Betalib.GetContestResultsFromTable($table);
+  const latestContestResult = getLatestContestResult(contestResults);
+  // 一度も参加したことがない
+  if (latestContestResult === null) {
+    return;
+  }
+  const tweetContent = makeTweetText(latestContestResult, isHighest(latestContestResult, contestResults));
+  const text = navigator.language === 'ja' ? '最新のコンテスト結果をツイート' : 'Tweet the result of the latest contest';
+  const $tweetButton = $('<a>').addClass('tweet').text(text)
+    .prop('href', `https://twitter.com/share?url=''&text=${encodeURIComponent(tweetContent)}`)
+    .prop('target', '_blank');
+  if (isDetailPage) {
+    $('#history_wrapper > div.row:first-child > .col-sm-6:first-child').eq(0).prepend($tweetButton);
+  }
+});
diff --git a/src/content/betalib.ts b/src/content/betalib.ts
index dcf69cc..d9160fd 100644
--- a/src/content/betalib.ts
+++ b/src/content/betalib.ts
@@ -122,6 +122,45 @@ export class JudgeStatus {
   }
 }
 
+export abstract class ContestResult {
+  constructor(public readonly date: Date, public readonly contestName: string, public readonly contestId: string, public readonly rank: number, public readonly diff: number) { }
+  abstract isRated(): boolean;
+  getRankStr(): string {
+    switch (this.rank % 10) {
+      case 1:
+        return `${this.rank}st`;
+      case 2:
+        return `${this.rank}nd`;
+      case 3:
+        return `${this.rank}rd`;
+      default:
+        return `${this.rank}th`;
+    }
+  }
+  getDiffStr(): string {
+    if (this.diff > 0) {
+      return `+${this.diff}`;
+    }
+    if (this.diff < 0) {
+      return this.diff.toString();
+    }
+    return '±0';
+  }
+}
+export class UnRatedContestResult extends ContestResult {
+  isRated() {
+    return false;
+  }
+}
+export class RatedContestResult extends ContestResult {
+  constructor(date: Date, contestName: string, contestId: string, rank: number, diff: number, public readonly performance: number, public readonly newRating: number) {
+    super(date, contestName, contestId, rank, diff);
+  }
+  isRated() {
+    return true;
+  }
+}
+
 export function parseJudgeStatus(text: string): JudgeStatus {
   const reg = /[　\s]/g;
   // WJ
@@ -230,3 +269,32 @@ export async function getProblems(): Promise<Problem[]> {
   });
   return res;
 }
+
+export function GetContestResultsFromTable($table: JQuery<HTMLElement>): ContestResult[] {
+  const res: ContestResult[] = [];
+  const $th = $('thead > tr > th', $table);
+  const indexes = getIndexes($th, {
+    date: ['Date', '日付'],
+    contest: ['Contest', 'コンテスト'],
+    rank: ['Rank', '順位'],
+    performance: ['Performance', 'パフォーマンス'],
+    newRating: ['NewRating', '新Rating'],
+    diff: ['Diff', '差分'],
+  });
+  $('tbody > tr', $table).each((idx, tr) => {
+    const $tds = $(tr).children('td');
+    const date = new Date($tds.eq(indexes.date).text());
+    const $contest = $tds.eq(indexes.contest).children('a').eq(0);
+    const contestName = $contest.text();
+    const contestId = (($contest.prop('href') as string).match(/\/contests\/([^\/]+)\/?$/) as string[])[1];
+    const rank = Number($tds.eq(indexes.rank).text());
+    const performanceStr = $tds.eq(indexes.performance).text();
+    const newRatingStr = $tds.eq(indexes.newRating).text();
+    const diff = Number($tds.eq(indexes.diff).text().replace(/[^0-9]/g, ''));
+    const isRated = performanceStr !== '-';
+    res[idx] =
+      isRated ? new RatedContestResult(date, contestName, contestId, rank, diff, Number(performanceStr), Number(newRatingStr))
+        : new UnRatedContestResult(date, contestName, contestId, rank, diff);
+  });
+  return res;
+}
diff --git a/src/css/add-twitter-button.css b/src/css/add-twitter-button.css
new file mode 100644
index 0000000..4171fb1
--- /dev/null
+++ b/src/css/add-twitter-button.css
@@ -0,0 +1,9 @@
+.row {
+  display: flex;
+  justify-content: space-between;
+}
+.tweet {
+  padding: 3px;
+  background-color: hsl(220, 70%, 60%);
+  color: white;
+}
diff --git a/src/css/add-twitter-button.less b/src/css/add-twitter-button.less
new file mode 100644
index 0000000..3bf1851
--- /dev/null
+++ b/src/css/add-twitter-button.less
@@ -0,0 +1,25 @@
+#history_wrapper > .row {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+}
+
+.tweet {
+  display: inline-block;
+  padding: 5px;
+  background-color: hsl(220, 70%, 60%);
+  border-radius: 3px;
+  color: white;
+  text-decoration: none;
+  transition: all .2s;
+  &:hover,
+  &:active,
+  &:focus,
+  &:visited {
+    color: white;
+    text-decoration: none;
+  }
+  &:hover {
+    background-color: hsl(220, 70%, 50%);
+  }
+}
diff --git a/src/manifest.json b/src/manifest.json
index ec0407c..35bab6e 100755
--- a/src/manifest.json
+++ b/src/manifest.json
@@ -1,35 +1,83 @@
 {
 	"name": "Comfortable Atcoder",
-	"version": "1.5.3",
+	"version": "1.5.4",
 	"manifest_version": 2,
-  "description": "Comfort your atcoder life. For more detail, visit https://github.com/drafear/comfortable-atcoder",
-  "author": "drafear",
+	"description": "Comfort your atcoder life. For more detail, visit https://github.com/drafear/comfortable-atcoder",
+	"author": "drafear",
 	"content_scripts": [
 		{
-			"matches": ["*://atcoder.jp/contests/*", "*://*.contest.atcoder.jp/*"],
-			"exclude_matches": ["*://*.contest.atcoder.jp/users/*"],
-			"js": ["lib/jquery.min.js", "lib/jquery.cookie.js", "content/all.js"],
-			"css": ["css/all.css"],
+			"matches": [
+				"*://atcoder.jp/contests/*",
+				"*://atcoder.jp/users/*",
+				"*://*.contest.atcoder.jp/*"
+			],
+			"exclude_matches": [
+				"*://*.contest.atcoder.jp/users/*"
+			],
+			"js": [
+				"lib/jquery.min.js",
+				"lib/jquery.cookie.js",
+				"content/all.js"
+			],
+			"css": [
+				"css/all.css"
+			],
 			"run_at": "document_start"
 		},
 		{
-			"matches": ["*://atcoder.jp/contests/*"],
-			"js": ["content/betalib.js", "content/dropdown-modify.js", "content/clar-notify.js"],
-			"css": ["css/dropdown-modify.css"],
+			"matches": [
+				"*://atcoder.jp/contests/*"
+			],
+			"js": [
+				"content/betalib.js",
+				"content/dropdown-modify.js",
+				"content/clar-notify.js"
+			],
+			"css": [
+				"css/dropdown-modify.css"
+			],
 			"run_at": "document_start"
 		},
 		{
-			"matches": ["*://atcoder.jp/contests/*/submissions/me"],
-			"js": ["content/result-notify.js"],
+			"matches": [
+				"*://atcoder.jp/contests/*/submissions/me"
+			],
+			"js": [
+				"content/result-notify.js"
+			],
 			"run_at": "document_start"
 		},
 		{
-			"matches": ["*://atcoder.jp/contests/*/submit*", "*://atcoder.jp/contests/*/tasks/*"],
-			"js": ["content/submission-warning.js"],
+			"matches": [
+				"*://atcoder.jp/contests/*/submit*",
+				"*://atcoder.jp/contests/*/tasks/*"
+			],
+			"js": [
+				"content/submission-warning.js"
+			],
+			"run_at": "document_start"
+		},
+		{
+			"matches": [
+				"*://atcoder.jp/users/*/history*"
+			],
+			"js": [
+				"content/add-tweet-button.js"
+			],
+			"css": [
+				"css/add-twitter-button.css"
+			],
+			"run_at": "document_start"
+		},
+		{
+			"matches": ["*://*.contest.atcoder.jp/*"],
+			"js": ["content/link-to-beta.js"],
 			"run_at": "document_start"
 		}
 	],
-	"web_accessible_resources": ["image/beta.png"],
+	"web_accessible_resources": [
+		"image/beta.png"
+	],
 	"background": {
 		"scripts": [
 			"lib/jquery.min.js",
@@ -42,7 +90,11 @@
 		"persistent": false
 	},
 	"options_page": "options-page/options.html",
-	"permissions": ["notifications", "storage", "<all_urls>"],
+	"permissions": [
+		"notifications",
+		"storage",
+		"<all_urls>"
+	],
 	"icons": {
 		"16": "image/icon.png",
 		"48": "image/icon.png",
diff --git a/src/options-page/options.js b/src/options-page/options.ts
similarity index 63%
rename from src/options-page/options.js
rename to src/options-page/options.ts
index 337e8ee..a5f0f09 100644
--- a/src/options-page/options.js
+++ b/src/options-page/options.ts
@@ -1,49 +1,47 @@
 class Language {
-  constructor(id, name) {
-    this.id = id;
-    this.name = name;
-  }
+  constructor(public readonly id: string, public readonly name: string) { }
 }
 
 class Switch {
-  constructor(onText, offText, storageKey, defaultValue = true) {
-    this.onText = onText;
-    this.offText = offText;
-    this.storageKey = storageKey;
+  public readonly defaultValue: boolean;
+
+  constructor(
+    public readonly onText: string,
+    public readonly offText: string,
+    public readonly storageKey: string,
+    defaultValue = true,
+  ) {
     this.defaultValue = defaultValue;
   }
 
-  readValue() {
-    return new Promise(
-      resolve => chrome.storage.sync.get(
-        [this.storageKey],
-        result => {
-          if (this.storageKey in result) {
-            resolve(Boolean(result[this.storageKey]));
-          } else {
-            chrome.storage.sync.set({[this.storageKey]: this.defaultValue});
-            resolve(this.defaultValue);
-          }
+  readValue(): Promise<boolean> {
+    return new Promise(resolve =>
+      chrome.storage.sync.get([this.storageKey], result => {
+        if (this.storageKey in result) {
+          resolve(Boolean(result[this.storageKey]));
+        } else {
+          chrome.storage.sync.set({ [this.storageKey]: this.defaultValue });
+          resolve(this.defaultValue);
         }
-      )
+      }),
     );
   }
 
-  cbChandeListener(e) {
-    const value = e.currentTarget.checked;
-    const data = {};
+  cbChangeListener(e: Event) {
+    const value = (e.currentTarget as HTMLInputElement).checked;
+    const data: { [key: string]: boolean } = {};
     data[this.storageKey] = value;
     chrome.storage.sync.set(data);
   }
 
   async toElem() {
-    const value = await this.readValue();
+    const value: boolean = await this.readValue();
     const label = document.createElement('label');
     label.classList.add('switch');
     const cb = document.createElement('input');
     cb.type = 'checkbox';
     cb.checked = value;
-    cb.addEventListener('change', this.cbChandeListener.bind(this));
+    cb.addEventListener('change', this.cbChangeListener.bind(this));
     label.appendChild(cb);
     const div = document.createElement('div');
     div.dataset.on = this.onText;
@@ -52,11 +50,8 @@ class Switch {
     return label;
   }
 }
-class Option {
-  constructor(name, component) {
-    this.name = name;
-    this.component = component;
-  }
+class Choice {
+  constructor(public readonly name: string, public readonly component: Switch) { }
 
   async toElem() {
     const li = document.createElement('li');
@@ -71,10 +66,7 @@ class Option {
 }
 
 class Group {
-  constructor(name, options) {
-    this.name = name;
-    this.options = options;
-  }
+  constructor(public readonly name: string, public readonly choices: Choice[]) { }
 
   async toElem() {
     const div = document.createElement('div');
@@ -83,7 +75,7 @@ class Group {
     div.appendChild(header);
     const ul = document.createElement('ul');
     ul.classList.add('settings-list');
-    for (const option of this.options) {
+    for (const option of this.choices) {
       ul.appendChild(await option.toElem());
     }
     div.appendChild(ul);
@@ -91,21 +83,16 @@ class Group {
   }
 }
 
-function makeWarnOptions(langs) {
+const makeWarnChoices = (langs: Language[]): Choice[] => {
   // Bash, Text
   const defaults = new Set(['3001', '3027']);
-  const options = [];
+  const choices: Choice[] = [];
   for (const lang of langs) {
     const defaultValue = Boolean(defaults.has(lang.id));
-    options.push(
-      new Option(
-        lang.name,
-        new Switch('on', 'off', `warn-${lang.id}`, defaultValue)
-      )
-    );
+    choices.push(new Choice(lang.name, new Switch('on', 'off', `warn-${lang.id}`, defaultValue)));
   }
-  return options;
-}
+  return choices;
+};
 
 const languages = [
   new Language('3003', 'C++14 (GCC)'),
@@ -167,48 +154,20 @@ const languages = [
 ];
 
 const groups = [
-  new Group(
-    'Non-beta',
-    [
-      new Option(
-        'Beta Tab',
-        new Switch('enable', 'disable', 'beta-tab'),
-      ),
-    ],
-  ),
-  new Group(
-    'Notification',
-    [
-      new Option(
-        'Judge Result',
-        new Switch('on', 'off', 'notify-judge-result'),
-      ),
-      new Option(
-        'Clarification',
-        new Switch('on', 'off', 'notify-clarification'),
-      ),
-    ],
-  ),
-  new Group(
-    'Dropdown',
-    [
-      new Option(
-        'Hover',
-        new Switch('hover', 'click', 'dropdown-hover'),
-      ),
-      new Option(
-        'Problem Tab',
-        new Switch('enable', 'disable', 'dropdown-problem'),
-      ),
-    ],
-  ),
-  new Group(
-    'Warning on Submission',
-    [
-      new Option('Enable', new Switch('enable', 'disable', 'submission-warning')),
-      ...makeWarnOptions(languages),
-    ],
-  ),
+  new Group('Non-beta', [new Choice('Beta Tab', new Switch('enable', 'disable', 'beta-tab'))]),
+  new Group('Notification', [
+    new Choice('Judge Result', new Switch('on', 'off', 'notify-judge-result')),
+    new Choice('Clarification', new Switch('on', 'off', 'notify-clarification')),
+  ]),
+  new Group('Dropdown', [
+    new Choice('Hover', new Switch('hover', 'click', 'dropdown-hover')),
+    new Choice('Problem Tab', new Switch('enable', 'disable', 'dropdown-problem')),
+  ]),
+  new Group('Tweet Button', [new Choice('Enable', new Switch('enable', 'disable', 'add-tweet-button'))]),
+  new Group('Warning on Submission', [
+    new Choice('Enable', new Switch('enable', 'disable', 'submission-warning')),
+    ...makeWarnChoices(languages),
+  ]),
 ];
 
 document.addEventListener('DOMContentLoaded', async () => {