Level

この issue には説明がありません。

The issue title 'Level' is vague; examine the Hangman game's existing codebase to understand how difficulty or progression might be implemented. Look for game logic files, possibly in a src/ or js/ directory, and check for any UI components related to game settings. Determine what a 'level' means in this context—difficulty, stages, or something else—by reviewing similar features in the repository or any related documentation.

索引モデルが issue の本文から書いたものです。