Objectives, campaign rules and scoring

Gameplay overview · World inventory · Native tables · Campaign code.

The normal Earth game and Other Worlds share much of the object machinery, but their campaign promotion rules differ. The expansion's manual is not a complete specification of the normal game's front end.

How missions are represented

Theatre files contain placed objects and their flags, qualities, velocities and timers. TWR text supplies airbase intelligence and optional Sxyth teleport starts. There is no separate per-briefing mission-script interpreter in the recovered objective path. A briefing's “destroy these targets”, “meet this spy” or “pass through these portals” is implemented by those objects and their handlers.

The catalogue lists all 25 pristine world variants, their environments and starts, and 339 stored objective-bearing anchors. It deliberately does not assign an object to whichever briefing start happens to be nearest: that would invent mission ownership absent from the files. Optional/preset-complete anchors are preserved, not counted as newly earned goals.

The engine's generator-orb quality table is the original manual's hqtbl. In normal 3.42 it lives at DS:ef93:

The native code adds detail beyond the short manual labels. Quality 2 includes Tets, and quality 8 checks both that an alien census has previously been nonzero and that the current checked count is zero. A completely unactivated alien area is not automatically treated as cleared.

bdbf is the shared completion operation. It sets live flag 0200h, increments the mission-objective statistic at DS:022c, and announces completion. It tests the bit first, preventing repeated credit. Every quality's satisfied and blocked paths, and repeated completion, are exercised in the native checks.

Local census and delayed completion

ba36 prepares counts from the preceding active-world pass and clears current counters; object handlers rebuild them during the next pass. Counts include separate KLA/AAA quality arrays and live fuel, vehicle, site, saucer, mindbender, Tet, alien and generator totals. Some peak/previous totals are retained.

The orb's own update (bce0–bd3e) selects its quality row and calls the goal handler only while its distance tier/key passes the eligibility test. The checked numbers are therefore tied to the streamed active neighbourhood and previous/current passes, not a global query over every stored object in the theatre.

This explains a documented and observable quirk: killing the targets does not necessarily light the complete indicator immediately. A return flyby of the orb or its wreck can allow its objective check to run. Destroying an orb also leaves a type-43 object whose handler still performs the applicable checks. The orb is not merely a target that disappears, taking its mission logic with it.

Forcefield shutdown similarly uses generator census. It is not implemented by explicit parent pointers linking each field to an orb. Preset completion and physical destruction are separate: a completed-but-intact orb can still power fields.

Other objective carriers and special bits

• A spy is a ground-crew object with 0800h set. Approaching on foot within 2000 cm changes its pose and invokes shared objective completion (8db1).
• A mission-objective saucer is type 53. Its damage handler invokes completion when the fatal branch is taken (c14c). Its ordinary saucer machinery remains.
• A portal may award completion in addition to its movement/damage action.
• Setting an anchor's complete bit in the builder makes it optional/already done; it does not create a new completion award during play.

The special bit is type-specific. For orbs it enables gravity attraction; for mindbenders it requires a planted-bomb lineage; for vehicles it restricts accepted attack types; for crew it identifies the spy. It is not one universal “stronger” or “hostile” flag.

Portals

The original xpqtbl is at DS:ee29. Each row has colour, flash colour, action bits and a signed damage/repair selector. A collision is acted on only for the player-aircraft sentinel and while the player is not on foot (c7ba).

Quality 6 deserves care: the manual's prose calls it a no-flash return, but its stored fourth word is 1, which the shared routine c78e handles as damage, just like quality 3. The table and consumer agree; the prose description is incomplete.

Relocation at 217b uses DS:02a9 for the base point, or randomized horizontal coordinates for the random action, and sets a new altitude. Do not interpret a portal as directly containing arbitrary destination coordinates.

Persistent worlds, aircraft and recovery

CORNCOB.BAT coordinates the menu and flight programs: menu selects state, flight runs, menu resumes with results. World modifications are repacked to compact records and saved with the campaign. Destroyed scenery, lost aircraft and remaining aircraft form the persistent campaign, rather than each sortie recreating its map. The already decoded .THT files show these changed worlds directly.

3UNIV.DAT is the shared working world passed between the DOS programs, not a master scenario definition. The front end associates the continued world with a pilot's numbered THT/*.THT campaign file; opening a fresh scenario or another saved theatre replaces the working world. Direct engine use can change the working file without updating PILOT.SCR, but this does not make its changes universal across every pilot and future fresh scenario. The save-file relationship and handoff sequence explain how PILOT.SCR, .THT and 3UNIV.DAT fit together.

The writer serializes 64 tile headers, the surviving compact object records and a twelve-byte starting-position trailer. Persistent changes can therefore include:

• Destroyed or removed scenery and enemies, wreck-type replacements and craters.
• Completed-objective bits, including the flags set by generator, spy and portal rules.
• Parked/abandoned aircraft records, their locations and persistent variant/damage flags.
• Positions, coarse orientations, flags, velocities and timers of saved world objects.
• Mission-builder edits, enabled UNIVBIN.DAT imports and the -e world-copy tool.
• Sky/ground colours committed with H+1/H+2, and changes to the stored starting point.

This is not a complete memory snapshot. encodeobj (F3DVEC.ASM:6997) writes position, three angle high bytes, flags, three velocity words, one timer word and type. It does not write the ordinary live hit-point byte at +27, so nonfatal object hit-point loss alone is not preserved by this format. Explicit wreck, removal, damage-flag and objective-state changes can be preserved. The flush path also excludes object types whose extended-property bit 0 is set: for example explosion, puff and projectile effects. Palette hallucination offsets themselves are not serialized; H+1/H+2 explicitly pack the selected base colours into the world header.

The normal engine saves on a clean campaign exit (3.ASM:11434), and also before the detailed-intelligence handoff (3.ASM:3157). H+1/H+2 update the in-memory header immediately but do not themselves call DOS file writing. See the palette setter and save-path trace.

Walking into another parked aircraft transfers its state into the player flight state (1e6a) and preserves a previous aircraft if necessary. Damaged/crashed planes and black experimental planes receive different ground-crew handling; ordinary spare planes are not equivalent to an unlimited respawn counter.

The control-tower proximity helper a610 uses the native distance helper's 1/64 scale, with tests at 5200 and 4200 units, about 3.328 km and 2.688 km. These update near-base and ground-crew/recovery-related state. Final landing/home status also depends on other flags and contact checks; being near any arbitrary radar model is not the complete return-home rule.

Entering a tower doorway on foot within 2000 cm raises the tower/report event (9887). The return-from-report path can restore the retained aircraft and repair state. A rescue van uses a separate close-range handoff and sets rescue status. This is why returning on foot, returning with the aircraft, a low flyby, landing, and rescue yield different outcomes and scores.

Exact score formula

The native score calculator is ISCORE.EXE, file offsets 4698–484f, normal retail 3.42. It accepts a pointer to the same 130-byte statistics block used by saved records. Original code, including Borland 32-bit multiplication/division, is executed by 72 controlled score probes.

Let quality indices q=1..8 refer to the displayed quality, and define:

primary = 15 * completed_objectives + fuel_or_tet_kills
          + sum(AAA_kills[q] + site_kills[q] + orb_kills[q])

danger = 10 + sum(q * (peak_AAA_count[q] + peak_KLA_count[q]))

raw = integer_divide(primary * danger * 5, 10)
      + sum(q * (KLA_kills[q] + vehicle_kills[q]))

score = integer_divide(raw * present_status_factor * sortie_status_factor,
                       planes_lost + 1)

The peak defence arrays are captured when weighted local defence totals exceed previous maxima. They are not numbers of kills. The score therefore rewards doing primary work in the presence of a more dangerous defence mix; secondary KLA/vehicle kills are quality-weighted and added afterward.

The native status-factor tests have priority, not just independent contributions:

Abort (4000h) returns score zero. The routine preserves legacy signed word intermediates and 32-bit arithmetic; the formula is a readable explanation for ordinary non-overflowing statistics, not permission to substitute unlimited-precision math and assume every corrupted/extreme record will behave the same.

Important statistics offsets relative to this 130-byte block:

Offsets here are hexadecimal. Site categories share some counters, so the display's “Other Sites” does not imply a unique counter for each visual type.

Medals: actual boundaries

Normal MOAG checks these at 1534a–15411; Other Worlds does so at 17d35–17dfc. Both supplied builds have the same tested score boundaries:

The manual says 10,000/20,000/50,000/100,000 begin the score awards, and says “more than 27” for the Purple Heart. The native comparisons differ at those exact boundaries. Eighteen score-boundary probes exercise both editions. Theatre Combat, Distinguished Flying Cross and Combat Master are checked by the preceding campaign completion scan, not these score bands.

Promotions differ between editions

Native probes isolate the promotion decision after campaign totals have been prepared. They do not substitute a fictitious filesystem into the theatre scanner.

Existing higher ranks are not demoted by this decision. Unused higher-rank text in the normal executable is therefore not proof that its normal promotion path awards those ranks. Both builds promote to Captain at seven, despite the manual listing eight. Other Worlds grants General in the all-required-theatres branch; there is no additional separate secret-mission flag test in that branch. Any prerequisite embodied in the required-theatre definitions is a separate question.

The underlying scan distinguishes required theatres, completed theatre records, and newly completed campaigns for medal reporting. It also preserves resurrection and pilot status. Every record field and all restrictions in that scanner are not yet independently decoded.

Ending, experimental aircraft and SRATS

The previously untraced SRATS.EXE has a confirmed gameplay call site. At 41ff–424b, the flight loop requires:

1. Aircraft flag 2000h, the black experimental variant.
2. The height word at DS:0e94 to reach the threshold at DS:027c.
3. The enabling flag at DS:0aec.

The theatre reader sets that threshold to three fifths of atmosphere height; the height comparison uses the position word spanning bits 8..23, approximately Z >> 8 in the ordinary positive altitude range. This is an altitude-based ending trigger, not a standard “all enemies dead” check.

After tearing down the normal display/timing state, the code calls 0d3b. That helper passes the literal filename srats.exe at DS:0d13 to the DOS program-launch wrapper. When it returns, the engine sets result bit 0400h and exits the sortie. Outcome selector de9d chooses panel 14, “You have saved Earth from alien attack!” That same result bit is what promotes the normal-game pilot to Major. This connects the experimental-plane ascent, starfield sequence, ending artwork and campaign promotion in actual code.

The command-line -f handler sets DS:0aec (d7a4). The same flag also unlocks throttle increases in the experimental aircraft (479c–47fe). With 2000h set and 0aec clear, the throttle-up input is ignored. Merely walking into the aircraft therefore does not grant permission to fly it.

The normal menu supplies f through its conditional argument builder at 112f2–11307. The condition is the pilot's Combat Master medal count at record offset 25eh, read by 15e5d–15e6e. That award is granted by the required- theatre completion scan. Once it has been earned, the ordinary throttle-up key works; there is no separate cockpit ignition sequence. Six native throttle probes confirm the gate, including unaffected normal and reserve aircraft.

The menu also contains the test-flight orders: report to White Sands, climb as high as possible, use the emergency rocket booster, then press Enter. This is stored briefing text; the native ending condition above is the actual trigger. The additional Enter press is not tested by that altitude branch.

Other ending panels are selected from flight status, not randomly: safe landing, rescue, crash landing, fatal crash, missing, capture, friendly-fire discipline and hazard-specific death. The handler at de59 distinguishes AA shell (type 22), KLA (type 24), crater (type 32) and other fatal contact for the corresponding panels. Friendly losses can add the military-police panel after a returned sortie.