Rule Enforcer

Or via exit_data on the Location:

# locations.py
connected_to=["Cerulean City"],   # Route 24 exit
# exploration.py checks game_data["badges"] before allowing movement

3. Story Flag Guard (one-time event)

# texts/en/exploration.py:
# MOON_STONE_FOUND: list[str] = [
#     "[bold yellow]★  You found a MOON STONE![/bold yellow]",
#     "[italic]You picked up a Moon Stone![/italic]",
# ]

# exploration.py — in show_arrival or explore_area callback
from pytemon.texts.en import exploration as T
from pytemon.ui.formatters import write_lines
flags = game_state.game_data["story_flags"]
if location_name == "Mt. Moon" and not flags.get("received_moon_stone"):
    flags["received_moon_stone"] = True
    bag = game_state.game_data["bag"]
    bag["Moon Stone"] = bag.get("Moon Stone", 0) + 1
    write_lines(output, T.MOON_STONE_FOUND)
# Second visit: flag is True, block skips, no duplicate item

4. Item Use Restriction

from pytemon.texts.en import items as T
from pytemon.ui.formatters import write_lines_fmt

# items.py
if item_name == "Thunder Stone":
    valid_species = {"PIKACHU", "EEVEE"}   # only these can use it
    if pokemon["species"] not in valid_species:
        write_lines_fmt(
            output,
            T.CANNOT_USE_ITEM_ON_POKEMON,
            name=pokemon["name"],
            item="Thunder Stone",
        )
        return

5. Checklist Before Adding a New Rule

• Story flag key is a meaningful snake_case string (e.g. "rival_cerulean_beaten")
• Flag is set exactly once — guard with if not flags.get("flag_name")
• Player sees a helpful message explaining the block (not a silent no-op)
• Rule is bypassed by game_state.cheat_mode if it's a movement gate

6. Output

• The guard code snippet + flag key
• The failure message string (Rich formatted)
• Where to insert the code (file and function)

Examples

Input: "Block Route 24 until player has Cascade Badge."

Output:

# texts/en/exploration.py:
# ROUTE24_BLOCKED: list[str] = [
#     "[yellow]A trainer blocks the way: 'You need the Cascade Badge!'[/yellow]",
# ]

from pytemon.texts.en import exploration as T
from pytemon.ui.formatters import write_lines

# exploration.py — in move_to_location, after resolving destination
if destination.lower() == "route 24":
    if "cascade" not in game_state.game_data.get("badges", []):
        if not game_state.cheat_mode:
            write_lines(output, T.ROUTE24_BLOCKED)
            return

Dependencies

• pytemon/exploration.py — movement and arrival logic
• pytemon/items.py — item use restrictions
• pytemon/game_state.py — game_data["story_flags"], game_data["badges"], cheat_mode

Error Handling

• Flag never set: trace back to where the preceding event (gym win, story beat) should set it
• CheatMode bypass forgotten: always wrap hard blocks with if not game_state.cheat_mode
• Rule fires on repeat visits: ensure the flag is set before the reward so the guard fires correctly next time