diff --git a/.vscode/settings.json b/.vscode/settings.json
index b75fabb..0967ef4 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,22 +1 @@
-{
-    "workbench.colorCustomizations": {
-        "activityBar.activeBackground": "#2f7c47",
-        "activityBar.background": "#2f7c47",
-        "activityBar.foreground": "#e7e7e7",
-        "activityBar.inactiveForeground": "#e7e7e799",
-        "activityBarBadge.background": "#422c74",
-        "activityBarBadge.foreground": "#e7e7e7",
-        "commandCenter.border": "#e7e7e799",
-        "sash.hoverBorder": "#2f7c47",
-        "statusBar.background": "#215732",
-        "statusBar.foreground": "#e7e7e7",
-        "statusBarItem.hoverBackground": "#2f7c47",
-        "statusBarItem.remoteBackground": "#215732",
-        "statusBarItem.remoteForeground": "#e7e7e7",
-        "titleBar.activeBackground": "#215732",
-        "titleBar.activeForeground": "#e7e7e7",
-        "titleBar.inactiveBackground": "#21573299",
-        "titleBar.inactiveForeground": "#e7e7e799"
-    },
-    "peacock.color": "#215732"
-}
+{}
diff --git a/src/app.ts b/src/app.ts
index e69de29..a58edf1 100644
--- a/src/app.ts
+++ b/src/app.ts
@@ -0,0 +1,140 @@
+// 70. シングルトン & private コンストラクタ
+abstract class Department {
+    static fiscalYear = 2020;
+
+    protected employees: string[] = [];
+
+    static createEmployee(name: string) {
+        return { name: name };
+    }
+
+    constructor(protected readonly id: string, public name: string) {
+        console.log(Department.fiscalYear);
+    }
+
+    abstract describe(this: Department): void;
+
+    addEmployee(employee: string) {
+        this.employees.push(employee);
+    }
+
+    printEmployeeInformation() {
+        console.log(this.employees.length);
+        console.log(this.employees);
+    }
+}
+
+class ITDepartment extends Department {
+    admins: string[];
+    constructor(id: string, admins: string[]) {
+        super(id, 'IT')
+        this.admins = admins;
+    }
+
+    describe() {
+        console.log('IT部門 - ID: ' + this.id);
+
+    }
+}
+
+class AccountingDepartment extends Department {
+    private lastReport: string;
+
+    // インスタンスを保持しておくためのprivateなstaticフィールドを追加する
+    //  以下はインスタンスというプロパティ名
+    //      このクラス自体が持っているフィールをを表す
+    // privateなフィールドなのでこのクラスの中からのみアクセスできる
+    //  フィールドの方は、このクラスのオブジェクト
+    // getInstanceメソッドで使用する
+    private static instance: AccountingDepartment;
+
+    get mostRecentReport() {
+        if (this.lastReport) {
+            return this.lastReport
+        }
+
+        throw new Error("レポートが見つかりません。");
+    }
+
+    set mostRecentReport(value: string) {
+        if (!value) {
+            throw new Error("正しい値を設定してください");
+        }
+        this.addReport(value)
+    }
+
+    private constructor(id: string, private reports: string[]) {
+        super(id, 'Accounting')
+        this.lastReport = reports[0];
+    }
+
+    // クラスの内部からしかアクセスできない問題を解決するにはstaticメソッドを使ってオブジェクトを作成する
+    //  メソッド名に決まりはない
+    //  インスタンスがあるかどうかをチェックするメソッド
+    //      インスタンスがあれば既存のインスタンスを返す
+    static getInstance() {
+        if (this.instance) {
+            return this.instance;
+        }
+        // 以下でもできる
+        // if (AccountingDepartment.instance) {
+        //     return this.instance;
+        // }
+        this.instance = new AccountingDepartment('d2', []);
+        return this.instance;
+    }
+
+    describe() {
+        console.log('会計部門 - ID: ' + this.id);
+    }
+
+    addReport(text: string) {
+        this.reports.push(text)
+        this.lastReport = text;
+    }
+
+    printReports() {
+        console.log(this.reports);
+    }
+
+    addEmployee(name: string) {
+        if (name === 'Max') {
+            return
+        }
+        this.employees.push(name);
+    }
+}
+
+const employee1 = Department.createEmployee('Max')
+console.log(employee1, Department.fiscalYear);
+
+
+const it = new ITDepartment('d1', ['Max']);
+
+
+it.addEmployee('Max')
+it.addEmployee('Manu')
+
+it.describe()
+it.printEmployeeInformation();
+
+console.log(it);
+// AccountingDepartmentのconstructorにprivateをするとnew AccountingDepartmentで以下のようなエラーが表示される
+//  Constructor of class 'AccountingDepartment' is private and only accessible within the class declaration.ts(2673)
+// const accounting = new AccountingDepartment('d2', []);
+const accounting = AccountingDepartment.getInstance();
+const accounting2 = AccountingDepartment.getInstance();
+
+console.log(accounting, accounting2);
+
+
+accounting.mostRecentReport = 'abc'
+accounting.addReport('Something')
+console.log(accounting.mostRecentReport);
+accounting.printReports()
+
+accounting.addEmployee('Max')
+accounting.addEmployee('Manu')
+
+accounting.describe()
+// accounting.printEmployeeInformation();
diff --git a/src/currentBackup.ts b/src/currentBackup.ts
new file mode 100644
index 0000000..e69de29
diff --git a/src/previousBackup.ts b/src/previousBackup.ts
new file mode 100644
index 0000000..e69de29