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Cape Cod patch v1.0 — TftD Lobster Man balance patcher
Reversible, backup-first, verify-before-write patcher fixing the hidden undocumented Lobster Man damage resistances (Phase 1) plus optional armor/health and weakest-weapon-power tweaks. Patcher + docs only; ships no game files. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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‎.gitignore‎

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# Never commit copyrighted game files or backups/output of the patcher.
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*.EXE
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*.exe
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*.DAT
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*.dat
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*.bak
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*.capecod.bak
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*.zip
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tftd/
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GAME_*/
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__pycache__/
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*.pyc
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.DS_Store

‎CAPE_COD_PATCH.md‎

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# The "Cape Cod" Patch — X-COM: Terror from the Deep
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> *Cape Cod is where lobsters go to die.*
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An unofficial, reversible balance micro-patch for the GOG/DOSBox release of
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**X-COM: Terror from the Deep** (1995). It edits the game's two DOS4GW
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executables and one data file **in place** (file sizes never change), so the
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game runs rebalanced through whatever launcher you already use. Every change is
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backed up and can be undone with a single command.
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---
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## The problems it fixes
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1. **Damage variance was narrowed.** TftD rolls all damage at 50–150% of weapon
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power (the original *UFO Defense* rolled firearms 0–200%). This inflates the
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value of armor and means even the weakest alien weapon (power 80) deals a
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*guaranteed* 40 on its minimum roll — instantly killing a fresh 40-HP rookie.
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2. **Lobster Men are near-unkillable** — heavy armor plus 100+ health let them
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shrug off almost anything and reaction-fire with impunity.
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3. **Lobster Men have a hidden, undocumented damage discount** applied *before*
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armor. It is shown nowhere in the game, not even on an M.C. scan. A "Heavy
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Gauss" reading 75 power was secretly doing ~22 before armor against a Lobster.
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---
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## What the patch changes
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The patch is **phased** so you apply only as much as you need. **Fixing the
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hidden resistances (Phase 1) alone is a 2×–5× increase in damage dealt to
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Lobsters and resolves most of the problem** — so it is the default, and the
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health/armor and weapon-power tweaks are opt-in.
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### Phase 1 (default) — Hidden resistance normalization · `TACTICAL.EXE`
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The Lobster Man's secret pre-armor damage multipliers, restored to a flat 100%:
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| Damage type | Vanilla | Cape Cod |
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|--------------------|:-------:|:--------:|
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| Armor-Piercing (guns) | 20% | **100%** |
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| Incendiary | 30% | **100%** |
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| High Explosive | 30% | **100%** |
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| Gauss | 30% | **100%** |
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| Sonic | 50% | **100%** |
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| Stun | 110% | unchanged |
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| Melee | 200% | unchanged |
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| Electric | 0% | unchanged |
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Natural weaknesses (Stun, Melee) and the Electric immunity are deliberately left
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alone — they don't make Lobsters tankier.
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**Effect, before armor:**
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| Weapon (power) | vs. Lobster, vanilla | vs. Lobster, patched |
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|-----------------------|:--------------------:|:--------------------:|
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| Gauss Rifle Clip (60) | ×0.30 → ~18 | ×1.00 → ~60 |
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| Heavy Gauss Clip (75) | ×0.30 → ~22 | ×1.00 → ~75 |
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| Sonic Clip (80) | ×0.50 → ~40 | ×1.00 → ~80 |
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| S. Cannon Clip (130) | ×0.50 → ~65 | ×1.00 → ~130 |
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Your weapons now do what their stats say they do.
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### Phase 2 (opt-in: `--with-armor-hp`) — Modest toughness trim · `GEOSCAPE.EXE`
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Applied across all six Lobster Man ranks:
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- **Front & side armor** trimmed (20 → 14; the toughest rank 22 → 16). Rear and
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under armor left as-is.
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- **Health** reduced by 20 per rank (e.g. 110 → 90, …, 135 → 115).
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This is a secondary tuning knob. With Phase 1 already multiplying your damage,
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you may not need it at all — try Phase 1 first.
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### Phase 3 (opt-in: `--with-weapon-power`) — Weakest-weapon power · `OBDATA.DAT`
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- **Sonic Clip** (the ammo for the Sonic Pistol, the weakest alien sonic weapon)
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power **80 → 66**. Its minimum 50% roll drops from 40 to 33, so a glancing hit
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no longer auto-kills a 40-HP rookie.
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> **Trade-off:** weapon stats in `OBDATA.DAT` apply to *everyone*, so a Sonic
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> Pistol the player later captures also reads power 66. This is an accepted cost
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> of fixing early-game lethality without touching the hardcoded damage formula.
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> (Per design choice, the 50–150% variance formula itself is **not** patched.)
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---
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## Usage
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Run from the `cape-cod` folder (the one containing this file):
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```bash
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python3 cape_cod_patch.py # Phase 1 only (recommended v1.0)
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python3 cape_cod_patch.py --with-armor-hp # Phase 1 + 2
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python3 cape_cod_patch.py --with-weapon-power # Phase 1 + 3
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python3 cape_cod_patch.py --full # all phases
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python3 cape_cod_patch.py --dry-run # preview the diff, write nothing
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python3 cape_cod_patch.py --verify # report what's currently applied
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python3 cape_cod_patch.py --revert # restore originals from backup
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```
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No dependencies — just Python 3.
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### Safety
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- **Backups:** on first write, each file is copied to `*.capecod.bak` (e.g.
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`TACTICAL.EXE.capecod.bak`). Backups are created once and never overwritten.
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- **Verify-before-write:** every edit is checked against a wide window of
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surrounding bytes. If they don't match (a different game build, a fan patch,
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offset drift), the patcher prints exactly what it expected vs. found and exits
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**without writing anything**.
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- **Idempotent:** re-running is safe — already-applied edits are detected and
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skipped.
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- **Reversible:** `--revert` restores the originals byte-for-byte (verified:
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post-revert checksums match the untouched files exactly).
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---
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## Verifying it works
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The patcher self-verifies structurally after every run (re-reads each offset,
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confirms the new values, and confirms file sizes are unchanged).
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For an in-game check, launch the game the way you normally do — the patched
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executables are already in place — start a tactical mission with Lobster Men,
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and confirm:
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- **Phase 1:** Gauss / conventional fire now visibly wounds Lobsters instead of
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registering a string of near-zeros; a Lobster falls in a sensible number of
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solid hits.
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- **Phase 3 (if applied):** a fresh rookie can survive a glancing hit from the
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weakest alien Sonic weapon instead of dying to the minimum roll.
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If after a mission or two Lobsters still feel oppressive, add `--with-armor-hp`.
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If early rookie deaths are still rough, add `--with-weapon-power`.
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---
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## Files
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| File | Role | Touched by |
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|------|------|-----------|
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| `cape_cod_patch.py` | the patcher | — |
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| `tftd/UFO2EXE/TACTICAL.EXE` | battlescape (damage math) | Phase 1 |
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| `tftd/UFOEXE/GEOSCAPE.EXE` | strategy layer (unit stats) | Phase 2 |
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| `tftd/GEODATA/OBDATA.DAT` | item/weapon stats | Phase 3 |
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| `*.capecod.bak` | automatic backups | created on first write |
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## Technical notes (for the curious)
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- Lobster resistances live in a damage-modifier table in `TACTICAL.EXE` at file
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offset `0x61478` (just past a `26` marker). It is row-major: each row is one
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damage type, 14 columns are unit types, and **Lobster Man is column 10**.
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- Lobster per-rank stats live in `GEOSCAPE.EXE` from `0x770dc` as six 39-byte
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records: armor (front/side/rear/under) at the start, **health at offset +31**.
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- `OBDATA.DAT` is 80 records × 54 bytes; **weapon power is at record-relative
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offset 22**. The Sonic Clip is record 39.

‎LICENSE‎

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MIT License
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Copyright (c) 2026 michaeldtimpe
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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---
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NOTE: This license covers ONLY the patch script and documentation in this
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repository. It does NOT cover, and this repository does NOT distribute, any
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part of X-COM: Terror from the Deep. That game and its data/executable files
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are the property of their respective copyright holders (Take-Two / 2K). You
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must own a legal copy of the game to use this patch.

‎README.md‎

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# The Cape Cod Patch — X-COM: Terror from the Deep
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> *Cape Cod is where lobsters go to die.* 🦞
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A small, reversible, **backup-first** balance patch for **X-COM: Terror from the
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Deep** (1995). It edits the game's own executables and data file *in place* (file
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sizes never change) to fix three long-standing imbalances — most importantly the
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**hidden, undocumented damage resistances** that make Lobster Men feel
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unkillable.
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This repository contains **only the patcher and documentation**. It does **not**
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include or distribute any game files — the patcher edits a copy of the game that
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**you already own**. You need a legal copy of *Terror from the Deep* (e.g. the
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GOG/DOS release).
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## What it fixes
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1. **Hidden Lobster Man resistances** — secret pre-armor damage discounts (only
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20% from guns, 30% from Gauss/explosives, 50% from Sonic) that are shown
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*nowhere* in-game. Normalized to 100%.
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2. **Lobster toughness** — modest armor + health trim (opt-in).
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3. **Weak-hit lethality** — the weakest alien weapon's minimum roll could
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one-shot a 40-HP rookie; its power is nudged down (opt-in).
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Full details, the resistance table, and the damage math are in
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[`CAPE_COD_PATCH.md`](CAPE_COD_PATCH.md).
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## Install
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1. Make sure you have **Python 3** (no other dependencies).
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2. Copy `cape_cod_patch.py` into your game install so that the script sits
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**next to the `tftd/` folder** that contains `UFO2EXE/`, `UFOEXE/`, and
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`GEODATA/`. (On the GOG release this is the main install directory.)
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- If your install lays the files out differently, edit the `TFTD_DIR` /
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`FILES` paths at the top of the script.
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## Usage
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```bash
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python3 cape_cod_patch.py # Phase 1 only (recommended)
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python3 cape_cod_patch.py --with-armor-hp # Phase 1 + armor/health trim
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python3 cape_cod_patch.py --with-weapon-power # Phase 1 + weakest weapon nerf
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python3 cape_cod_patch.py --full # everything
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python3 cape_cod_patch.py --dry-run # preview the diff, write nothing
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python3 cape_cod_patch.py --verify # report what's applied
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python3 cape_cod_patch.py --revert # restore originals from backup
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```
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**Start with Phase 1.** Normalizing the hidden resistances alone is a 2×–5×
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increase in damage dealt to Lobsters and fixes most of the problem; the other
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phases are optional tuning.
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## Safety
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- **Backups:** every touched file is copied to `*.capecod.bak` on first write
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(created once, never overwritten).
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- **Verify-before-write:** each edit is checked against a wide window of
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surrounding bytes. If they don't match (different build, fan patch, offset
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drift) the patcher prints what it expected vs. found and **writes nothing**.
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- **Reversible:** `--revert` restores the originals byte-for-byte.
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- **Idempotent:** re-running is safe.
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## Disclaimer
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Unofficial, fan-made, and not affiliated with or endorsed by Take-Two / 2K or
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the original developers. Use at your own risk. *X-COM: Terror from the Deep* and
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all related assets are the property of their respective copyright holders.

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