Analysis and reimplementation of Railroad Tycoon 3


The old executable is at ./rt3_wineprefix/drive_c/rt3/RT3.exe

Our first task is to understand the executable's high-level control loops and subsystem boundaries well
enough to choose good rewrite targets. As we go, we document evidence, keep a curated function map,
and stand up Rust tooling that can validate artifacts and later host replacement code.

The long-term direction is still a DLL we can inject into the original executable, patching in
individual functions as we build them out. The active implementation milestone is now a headless
runtime rehost layer that can execute deterministic world work, compare normalized state, and grow
subsystem breadth without depending on the shell or presentation path. The current packed-event
frontier is broader real grouped-descriptor coverage on top of the existing save-slice, snapshot,
overlay-import, compact-control, and symbolic company-target workflows. The runtime already carries
selected-company and controller-role context through overlay imports, and real descriptors `2`
`Company Cash`, `13` `Deactivate Company`, and `16` `Company Track Pieces Buildable` now parse and
execute through the ordinary runtime path, and descriptors `1` `Player Cash` and `14`
`Deactivate Player` now join that batch through the same service engine. Synthetic packed records
still exercise the same runtime without a parallel packed executor. The first grounded
chairman-profile runtime slice now exists too: save-slice or overlay-backed chairman/company
context plus the hidden grouped target-subject lane let those same real descriptors `1` and `14`
execute on the grounded chairman scope ordinals `0..3` (`condition_true`, `selected`, `human`,
`ai`), while wider chairman ordinals remain explicit parity. The first grounded
chairman and governance condition batch is broader now: selected-chairman cash / holdings / net
worth / purchasing-power thresholds and company book-value-per-share / investor-confidence /
management-attitude thresholds now import through the normal event-service path, while wider
chairman ordinals remain explicit frontier. Checked-in save-slice
documents can now also carry explicit company rosters and chairman-profile tables, so the current
company-targeted and chairman-targeted descriptor and condition batches can execute from standalone
save-slice fixtures without overlay snapshots when that context is present; raw `.gms` inspection
still does not reconstruct those company/chairman collections automatically, but it now does
reconstruct selection-only company/chairman context from the fixed save-side `0x32c8` world block.
Those raw selected ids can flow through save-slice export/import and override overlay-backed base
selection even while the full raw rosters remain absent, and a tracked overlay fixture now pins
that selection-only override path explicitly. The same fixed block now also exports the grounded
campaign override byte plus the raw chairman slot selector and role-gate bytes as analysis-only
save fields. Raw `.gms` inspection now also lifts the save-side tagged header counts for the
company and chairman/profile collections into `observed_entry_count`, so save-slice exports carry
header-level roster counts alongside the selected ids even while per-entry payload remains
unreconstructed. A checked-in
`EventEffects` export now exists too in
`artifacts/exports/rt3-1.06/event-effects-table.json`, and a checked-in semantic closure layer now
exists beside it in `artifacts/exports/rt3-1.06/event-effects-semantic-catalog.json`. Recovered
descriptor rows now land on explicit semantic frontier buckets such as
`blocked_shell_owned_descriptor`, `blocked_evidence_blocked_descriptor`, and
`blocked_variant_or_scope_blocked_descriptor` instead of generic anonymous descriptor residue. The
first recovered governance descriptor tranche now imports through the generic
company-governance scalar effect surface:
descriptor `56` `Credit Rating` and descriptor `57` `Prime Rate` execute from ordinary real packed
rows, while adjacent recovered finance/control-transfer descriptors such as `55` `Stock Prices`
and `58` `Merger Premium` now land on explicit shell-owned parity instead of anonymous unmapped
descriptor residue, and tracked shell-owned fixtures now pin finance, scenario-outcome, and
control-transfer shell rows explicitly. The
recovered whole-game scalar economy/performance strip `59..104` now has a
bounded runtime landing surface too: representative descriptors import into
`RuntimeState.world_scalar_overrides` through stable normalized keys such as
`world.build_stations_cost`, `world.track_maintenance_cost`, `world.all_engine_speeds`, and
`world.hotel_revenue`. The runtime-variable strip `39..54` now executes too through bounded
event-owned scalar maps on world/company/player/territory state, and the matching ordinary
condition strip now gates records through those same maps too, without widening save-native
reconstruction or adding a second packed executor. The grounded aggregate cargo-economics
descriptors now have bounded
runtime landing surfaces too: descriptor `105` `All Cargo Prices` plus descriptors `177..179`
`All Cargo Production` / `All Factory Production` / `All Farm/Mine Production` import into
event-owned cargo override state, and the grounded named cargo-production strip `180..229` now
imports into named cargo production overrides too, and the named cargo-price strip `106..176` now
imports into named cargo price overrides as well. The checked-in static selector reconstruction is
now explicit: the broader 1.06 CargoTypes corpus has `51` names, the Cargo106 `cargoSkin` corpus
has `70`, and the rehosted offline selector builder now closes the `71`-row named price strip as
`cargoSkin` plus the core `Rock` carry-over. The checked-in
`artifacts/exports/rt3-1.06/economy-cargo-sources.json` report parses both `CargoTypes` and the
`Cargo106.PK4` `cargoSkin` descriptors, normalizes localized `~####Name` tokens into visible
names, builds a merged live cargo registry, and now derives exact named cargo-production and named
cargo-price selectors from the checked-in bindings. Dedicated CLI inspector commands now expose
both grounded selectors directly, while the same report still makes the residual live-registry gap
explicit by showing the nine excluded CargoTypes-only industrial names outside the 71-row price
strip. The
add-building strip `503..519` is now explicitly classified as recovered
shell-owned descriptor parity rather than generic unresolved residue. The first grounded
condition-side unlock now exists for negative-sentinel `raw_condition_id = -1` company scopes, and
the first ordinary nonnegative condition batch now executes too: numeric-threshold company
finance, company track, aggregate territory track, and company-territory track rows can import
through overlay-backed runtime context. Exact named-territory binding now executes, and the runtime
now also carries the minimal event-owned train roster and opaque economic-status lane needed for
real descriptors `8` `Economic Status`, `9` `Confiscate All`, and `15` `Retire Train` to execute
through the same path. Descriptor `3`
`Territory - Allow All` now executes too, reinterpreted as company-to-territory access rights
rather than a territory-owned policy bit. Whole-game ordinary-condition execution now exists too:
special-condition thresholds, candidate-availability thresholds, and economic-status-code
thresholds now gate imported runtime records through the same service path, and that world-side
condition batch now decodes from checked-in metadata instead of fixture-only ids: real
special-condition label ids, real economic-status ids, and the recovered `%1 Avail.` candidate
template plus candidate-name side strings all lower into the runtime condition model. Checked-in
whole-game descriptor metadata now drives the first real world-side effect batch too:
special-condition and candidate-availability setters import natively, and descriptor `110`
`Disable Stock Buying and Selling` now lowers into the keyed runtime flag
`world.disable_stock_buying_and_selling`. The recovered whole-game toggle batch is broader now
too: descriptors `111..138`, with descriptor `122` `Limited Track Building Amount` now landing in
the bounded `world_restore.limited_track_building_amount` scalar and the remaining boolean lanes
lowering into keyed `world_flags`, cover finance/trading, construction, and governance
restrictions. Explicit the late recovered special-condition toggles now execute too where current
evidence is equally
strong: `Use Bio-Accelerator Cars`, `Disable Cargo Economy`, `Disable Train Crashes`, `Disable
Train Crashes AND Breakdowns`, and `AI Ignore Territories At Startup`. Whole-game condition decode
is broader now too: checked-in world-flag condition ids can lower into `world_flag_equals` gates
for boolean equality/inequality forms, so real packed records can gate whole-game effects on
existing `world_flags` without fixture-authored placeholder ids. The tracked parity save-slice no
longer depends on a raw `unsupported_framing` placeholder either: its remaining residue is now one
recovered locomotives-page `real_packed_v1` record that now lands on explicit descriptor parity
instead of a generic unmapped bucket. The next recovered descriptor band is now partially
executable too: descriptors `454..456` (`All Steam/Diesel/Electric Locos Avail.`) now lower
through checked-in metadata into keyed `world_flags`, while the wider locomotive availability/cost
scalar bands are now save-native too. Raw `.smp` inspection/export reconstructs the persisted
`[world+0x66b6]` locomotive name table and derives a minimal `RuntimeState.locomotive_catalog`, so
standalone save-slice imports can now lower the grounded lower locomotive availability and
locomotive-cost rows directly into `RuntimeState.named_locomotive_availability` and
`RuntimeState.named_locomotive_cost` without needing overlay snapshots when the save carries enough
catalog context, and the grounded executable lower prefix now extends through save-backed
locomotive id `61` (`Zephyr`); the unresolved lower tail and upper locomotive bands now stay on
explicit parity instead of synthetic execution. The remaining recovered scalar world families
execute too:
cargo-production slots `230..240` lower into `cargo_production_overrides`, and descriptor `453`
lowers into
`world_restore.territory_access_cost`. Whole-game ordinary-condition breadth now aligns with those
same world-scalar runtime surfaces too: named locomotive availability thresholds, named
locomotive cost thresholds, named cargo-production slot thresholds, aggregate cargo-production
thresholds, factory/farm-mine/other cargo-production thresholds, limited-track-building-amount
thresholds, and territory-access-cost thresholds all gate imported runtime records through the
same service path. Explicit unmapped world-condition frontier buckets still remain where current
checked-in metadata stops, and
`blocked_missing_locomotive_catalog_context` is now reserved for intentionally incomplete save-side
catalog context instead of the normal save-slice path. Cargo slot identity and class metadata are
now save-native too: the recipe-book probe lowers into `RuntimeState.cargo_catalog`, so save-slice
documents can carry slot labels, class tags, and token-stem evidence alongside the executable
`cargo_production_overrides` surface without introducing a live cargo-economy model. Shell
purchase-flow, Trainbuy refresh,
cached locomotive-rating recomputation, and selected-profile parity remain out of scope. Mixed
supported/unsupported real rows still stay parity-only. The PE32 hook remains useful as capture and
integration tooling, but it is no longer the main execution milestone.

## Project Docs

Bootstrap design and workflow documents live in `docs/`.

- `docs/README.md`: handbook index and target hashes
- `docs/control-loop-atlas.md`: compatibility index for the split atlas
- `docs/control-loop-atlas/`: canonical atlas section files
- `docs/setup-workstation.md`: toolchain baseline and local setup
- `docs/re-workflow.md`: repeatable reverse-engineering workflow
- `docs/function-map.md`: canonical function-map schema and conventions

The first committed exports for the canonical 1.06 executable live in `artifacts/exports/rt3-1.06/`.

## Rust Workspace

The Rust workspace is split into focused crates:

- `rrt-model`: shared types for addresses, function-map rows, and control-loop concepts
- `rrt-runtime`: headless runtime state, stepping, normalized event service, and persistence-facing
  runtime types
- `rrt-fixtures`: fixture schemas, loading, normalization, and diff helpers for rehost validation
- `rrt-cli`: validation, runtime fixture execution, state-diff tools, and repo-health checks
- `rrt-hook`: minimal Windows DLL scaffold for low-risk in-process loading, capture, and later
  integration experiments under Wine

For the current headless runtime smoke path, use `cargo run -p rrt-cli -- runtime summarize-fixture
fixtures/runtime/minimal-world-step-smoke.json` or one of the broader runtime fixtures under
`fixtures/runtime/`.

For the current hook smoke test, run `tools/run_hook_smoke_test.sh`. It builds the PE32 proxy,
copies it into the local RT3 install, launches the game briefly under Wine with
`WINEDLLOVERRIDES=dinput8=n,b`, and expects `rrt_hook_attach.log` to appear.
