freeski_flag_extract.py

#!/usr/bin/env python3
import random
import binascii

mountain_width = 1000  # same as in the game


class Mountain:
    def __init__(self, name, height, treeline, yetiline, encoded_flag):
        self.name = name
        self.height = height
        self.treeline = treeline
        self.yetiline = yetiline
        self.encoded_flag = encoded_flag
        self.treasures = self.GetTreasureLocations()

    def GetTreasureLocations(self):
        """
        Reimplementation of the game's treasure placement:
        - Deterministic per mountain name via crc32(name)
        - 5 treasures at decreasing elevations (down the mountain)
        - Each treasure has a horizontal position (can be out of bounds, later modded)
        """
        locations = {}
        random.seed(binascii.crc32(self.name.encode("utf-8")))
        prev_height = self.height
        prev_horiz = 0

        for _ in range(5):
            e_delta = random.randint(200, 800)
            h_delta = random.randint(int(0 - e_delta / 4), int(e_delta / 4))

            elevation = prev_height - e_delta
            horiz = prev_horiz + h_delta

            locations[elevation] = horiz

            prev_height = elevation
            prev_horiz = horiz

        return locations


def SetFlag(mountain, treasure_list):
    """
    Exact copy of the game's flag-decoding logic:

    product = (product << 8) ^ treasure_val
    random.seed(product)
    decoded_byte = encoded_flag[i] ^ random.randint(0, 255)
    """
    product = 0
    for treasure_val in treasure_list:
        product = (product << 8) ^ treasure_val

    random.seed(product)

    decoded_chars = []
    for b in mountain.encoded_flag:
        r = random.randint(0, 255)
        decoded_chars.append(chr(b ^ r))

    flag_text = "Flag: %s" % "".join(decoded_chars)
    return flag_text


# Recreate Mountains as in the decompiled code
Mountains = [
    Mountain(
        "Mount Snow",
        3586,
        3400,
        2400,
        b"\x90\x00\x1d\xbc\x17b\xed6S\"\xb0<Y\xd6\xce\x169\xae\xe9|\xe2Gs\xb7\xfdy\xcf5\x98",
    ),
    Mountain(
        "Aspen",
        11211,
        11000,
        10000,
        b"U\xd7%x\xbfvj!\xfe\x9d\xb9\xc2\xd1k\x02y\x17\x9dK\x98\xf1\x92\x0f!\xf1\\\xa0\x1b\x0f",
    ),
    Mountain(
        "Whistler",
        7156,
        6000,
        6500,
        b"\x1cN\x13\x1a\x97\xd4\xb2!\xf9\xf6\xd4#\xee\xebh\xecs.\x08M!hr9?\xde\x0c\x86\x02",
    ),
    Mountain(
        "Mount Baker",
        10781,
        9000,
        6000,
        b"\xac\xf9#\xf4T\xf1%h\xbe3FI+h\r\x01V\xee\xc2C\x13\xf3\x97ef\xac\xe3z\x96",
    ),
    Mountain(
        "Mount Norquay",
        6998,
        6300,
        3000,
        b"\x0c\x1c\xad!\xc6,\xec0\x0b+\"\x9f@.\xc8\x13\xadb\x86\xea{\xfeS\xe0S\x85\x90\x03q",
    ),
    Mountain(
        "Mount Erciyes",
        12848,
        10000,
        12000,
        b"n\xad\xb4l^I\xdb\xe1\xd0\x7f\x92\x92\x96\x1bq\xca`PvWg\x85\xb21^\x93F\x1a\xee",
    ),
    Mountain(
        "Dragonmount",
        16282,
        15500,
        16000,
        b"Z\xf9\xdf\x7f_\x02\xd8\x89\x12\xd2\x11p\xb6\x96\x19\x05x))v\xc3\xecv\xf4\xe2\\\x9a\xbe\xb5",
    ),
]


def compute_treasure_list(mountain: Mountain):
    """
    In-game, when you collide with a treasure at:
      - elevation = collided_row[0]
      - column    = collided_row_offset (0..mountain_width-1)
    it records: elevation * mountain_width + collided_row_offset

    We reconstruct the SAME values from the deterministic treasure map:
      - elevation is the key in mountain.treasures
      - horizontal index is (horiz % mountain_width)
    """
    treasure_values = []

    # Treasures are generated from top to bottom (highest to lowest elevation),
    # and the player will naturally encounter them in that order.
    # We emulate that ordering explicitly.
    for elevation, horiz in sorted(mountain.treasures.items(), key=lambda kv: kv[0], reverse=True):
        col = horiz % mountain_width
        treasure_val = elevation * mountain_width + col
        treasure_values.append(treasure_val)

    return treasure_values


def main():
    for mnt in Mountains:
        treasure_list = compute_treasure_list(mnt)
        flag = SetFlag(mnt, treasure_list)
        print(f"Mountain: {mnt.name}")
        print(f"  Treasures (elev, horiz_mod):")
        for elevation, horiz in sorted(mnt.treasures.items(), key=lambda kv: kv[0], reverse=True):
            print(f"    elevation={elevation}, horiz_mod={horiz % mountain_width}")
        print(f"  {flag}")
        print("-" * 60)


if __name__ == "__main__":
    main()