GRAV (Steam app 332500) expiry kill-switch patcher — fixes the 'App Expired' launch error by pinning the engine's calendar year to 2024. Pure Python 3, verifies the build, backs up, verifies result, supports --status/--undo.

patch_grav.py

#!/usr/bin/env python3
"""GRAV (Steam app 332500) — expiry kill-switch patcher.

GRAV's final build (buildid 1763174, Jan 2016) contains a hard-coded
expiry date check: after ~9 years it shows "App Expired - This app has
expired. Please get the latest update from steam." and quits, even for
valid owners. The check reads the calendar year through four engine
wrapper functions that all extract it with the same 6-byte instruction:

    44 0f b7 5c 24 20    movzx r11d, WORD PTR [rsp+0x20]   ; wYear

This script replaces each occurrence, same length, with:

    41 bb e8 07 00 00    mov r11d, 2024

so the engine reports year 2024 forever and the kill-switch never
trips. All other timekeeping (durations, timers, file times) is real.

Usage:
    patch_grav.py            ensure patched (backs up first run)
    patch_grav.py --status   just report the current state
    patch_grav.py --undo     restore the original from the backup
    patch_grav.py <path>     operate on a different copy of the exe
"""

import os
import re
import shutil
import stat
import sys
from pathlib import Path

if sys.platform.startswith("win"):
    DEFAULT_EXE = Path(os.environ.get("ProgramFiles(x86)", r"C:\Program Files (x86)")) / (
        "Steam/steamapps/common/GRAV/Binaries/Win64/CAGGame-Win64-Shipping.exe"
    )
else:
    DEFAULT_EXE = Path.home() / (
        ".local/share/Steam/steamapps/common/GRAV/Binaries/Win64/"
        "CAGGame-Win64-Shipping.exe"
    )

PATCH_FROM = bytes.fromhex("440fb75c2420")  # movzx r11d, WORD [rsp+0x20]
PATCH_TO = bytes.fromhex("41bbe8070000")    # mov r11d, 2024
EXPECTED_SITES = 4
BACKUP_SUFFIX = ".orig.bak"


def find(data: bytes, pat: bytes):
    return [m.start() for m in re.finditer(re.escape(pat), data)]


def main() -> int:
    args = [a for a in sys.argv[1:]]
    undo = "--undo" in args
    status_only = "--status" in args
    paths = [Path(a) for a in args if not a.startswith("--")]
    exe = paths[0] if paths else DEFAULT_EXE
    backup = exe.with_name(exe.name + BACKUP_SUFFIX)

    if not exe.is_file():
        print(f"ERROR: game executable not found: {exe}")
        print("Pass the path explicitly if GRAV is installed elsewhere.")
        return 1

    data = exe.read_bytes()
    unpatched = find(data, PATCH_FROM)
    patched = find(data, PATCH_TO)
    already = len(patched) >= EXPECTED_SITES and not unpatched

    print(f"Executable : {exe}")
    print(f"Size       : {len(data):,} bytes")
    print(f"Unpatched sites: {len(unpatched)}   patched sites: {len(patched)}")

    if undo:
        if not backup.is_file():
            print("ERROR      : no backup found, cannot undo.")
            return 1
        shutil.copy2(backup, exe)
        print("STATUS     : original executable restored from backup.")
        return 0
    if already:
        print("STATUS     : already patched (kill-switch disabled). Nothing to do.")
        return 0
    if status_only:
        print("STATUS     : not patched.")
        return 0

    if len(unpatched) != EXPECTED_SITES:
        print(
            f"ERROR      : expected exactly {EXPECTED_SITES} patch sites, "
            f"found {len(unpatched)}. This is probably a different build — "
            "aborting without changes."
        )
        return 1

    if not backup.is_file():
        shutil.copy2(exe, backup)
        print(f"Backup     : saved {backup.name}")
    else:
        print(f"Backup     : {backup.name} already exists, left untouched.")

    buf = bytearray(data)
    for off in unpatched:
        buf[off : off + len(PATCH_TO)] = PATCH_TO

    tmp = exe.with_name(exe.name + ".patching.tmp")
    tmp.write_bytes(buf)
    os.chmod(tmp, stat.S_IMODE(exe.stat().st_mode))
    tmp.replace(exe)

    verify = exe.read_bytes()
    if len(find(verify, PATCH_TO)) != len(unpatched) or find(verify, PATCH_FROM):
        print("ERROR      : verification failed! Restore from the backup.")
        return 1
    print(f"STATUS     : patched {len(unpatched)} sites. Kill-switch disabled.")
    print("Remember   : Steam 'Verify integrity of game files' will undo this;")
    print("             re-run this script afterwards to re-apply.")
    return 0


if __name__ == "__main__":
    sys.exit(main())