The enum is an original syntax of TypeScript (it does not exist in JavaScript). So it is converted to like the following form as a result of transpilation: ```js let OperatingSystem; (function (OperatingSystem) { OperatingSystem[OperatingSystem["MacOS"] = 0] = "MacOS"; OperatingSystem[OperatingSystem["Windows"] = 1] = "Windows"; OperatingSystem[OperatingSystem["Linux"] = 2] = "Linux"; })(OperatingSystem || (OperatingSystem = {})); ``` In this question, the type should convert a given string tuple to an object that behaves like an enum. Moreover, the property of an enum is preferably a pascal case. ```ts Enum<["macOS", "Windows", "Linux"]> // -> { readonly MacOS: "macOS", readonly Windows: "Windows", readonly Linux: "Linux" } ``` If `true` is given in the second argument, the value should be a number literal. ```ts Enum<["macOS", "Windows", "Linux"], true> // -> { readonly MacOS: 0, readonly Windows: 1, readonly Linux: 2 } ```by Ryo Hanafusa @softoika