The Cape Cod Patch — X-COM: Terror from the Deep

Cape Cod is where lobsters go to die. 🦞

A small, reversible, backup-first balance patch for X-COM: Terror from the Deep (1995). It edits the game's own executables and data file in place (file sizes never change) to fix three long-standing imbalances — most importantly the hidden, undocumented damage resistances that make Lobster Men feel unkillable.

This repository contains only the patcher and documentation. It does not include or distribute any game files — the patcher edits a copy of the game that you already own. You need a legal copy of Terror from the Deep (e.g. the GOG/DOS release).

What it fixes

1. Hidden Lobster Man resistances — secret pre-armor damage discounts (only 20% from guns, 30% from Gauss/explosives, 50% from Sonic) that are shown nowhere in-game. Normalized to 100%.
2. Lobster toughness — modest armor + health trim (opt-in).
3. Weak-hit lethality — the weakest alien weapon's minimum roll could one-shot a 40-HP rookie; its power is nudged down (opt-in).

Full details, the resistance table, and the damage math are in CAPE_COD_PATCH.md.

Install

1. Make sure you have Python 3 (no other dependencies).
2. Copy cape_cod_patch.py into your game install so that the script sits next to the tftd/ folder that contains UFO2EXE/, UFOEXE/, and GEODATA/. (On the GOG release this is the main install directory.)
   • If your install lays the files out differently, edit the TFTD_DIR / FILES paths at the top of the script.

Usage

python3 cape_cod_patch.py                       # Phase 1 only (recommended)
python3 cape_cod_patch.py --with-armor-hp       # Phase 1 + armor/health trim
python3 cape_cod_patch.py --with-weapon-power   # Phase 1 + weakest weapon nerf
python3 cape_cod_patch.py --full                # everything

python3 cape_cod_patch.py --dry-run             # preview the diff, write nothing
python3 cape_cod_patch.py --verify              # report what's applied
python3 cape_cod_patch.py --revert              # restore originals from backup

Start with Phase 1. Normalizing the hidden resistances alone is a 2×–5× increase in damage dealt to Lobsters and fixes most of the problem; the other phases are optional tuning.

Safety

• Backups: every touched file is copied to *.capecod.bak on first write (created once, never overwritten).
• Verify-before-write: each edit is checked against a wide window of surrounding bytes. If they don't match (different build, fan patch, offset drift) the patcher prints what it expected vs. found and writes nothing.
• Reversible: --revert restores the originals byte-for-byte.
• Idempotent: re-running is safe.

Disclaimer

Unofficial, fan-made, and not affiliated with or endorsed by Take-Two / 2K or the original developers. Use at your own risk. X-COM: Terror from the Deep and all related assets are the property of their respective copyright holders.