An adventures game where it can extend as much as you like.

Is your feature request related to a problem?
The repository currently lacks a text-based interactive adventure/choose-your-own-path game. This is a fun, beginner-friendly project type that's great for practicing conditionals, string input handling, and branching program flow — but it's also naturally suited to being extended collaboratively, since a text adventure can keep growing with new paths, endings, and story branches.

Describe the Solution
Add an adventure_game.py file implementing the initial skeleton of a text-based choose-your-own-adventure game where:

The player enters their name and receives a welcome message
The player faces a fork in a dirt road and chooses to go left or right
Left path leads to a river, where the player chooses to swim across (bad ending — eaten by an alligator) or walk around (bad ending — runs out of water)
Right path leads to an old bridge, where the player chooses to cross (good ending — successfully crosses) or head back (bad ending — gets lost)
Invalid inputs at any choice point are handled with a "Not a valid option" message

This is intentionally an open starting point, not a finished game. I'm submitting this as a base structure so that other contributors can extend it over time by:

Adding new branching paths and choices at each existing decision point
Adding entirely new story arcs/locations beyond the current two endings per path
Adding more "good" endings, items/inventory mechanics, or a scoring system
Refactoring the branching logic into functions/a scene-based structure as the story grows (to keep the code maintainable as more contributors add paths)

Describe Alternatives
An alternative would be to build out a fully complete game in a single PR before submitting. However, keeping it intentionally small and open-ended encourages community contribution and makes it easier for new/beginner contributors to add a single new path or ending as their first contribution to the repo.
Additional Context
This kind of project is a good "good first issue" magnet — new contributors can add a single elif branch and a couple of print statements without needing to understand the whole codebase, making it a great low-barrier entry point for first-time open source contributors.
Complexity

Simple (< 50 lines)
Medium (50-200 lines)
Complex (> 200 lines)

issue で説明されているテキストベースの Choose-your-own-adventure のエントリーポイントとして adventure_game.py を作成します。手動で実行し、名前の入力を求めること、左/右の道の選択肢とその結果を表示すること、無効な選択に対して "Not a valid option" と出力することを確認します。