Fuel gauge

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A fuel gauge limits how long an engine can run. The Pilotwings 64 gyrocopter burns fuel only while its engine is on, at a rate set by the throttle¹. Star Control II charges its flagship’s fuel by distance flown in HyperSpace, where Pilotwings 64 charges by time with the engine on^2,1. Each 16² logical units flown cost one charge, and 100² charges make one unit on the gauge.

Games

Game	Year	How	Note
Star Control II	1992	By distance	1/100 of a fuel unit for each 16 logical units flown in HyperSpace
Pilotwings 64	1996	By throttle	the gyrocopter's tank drains while the engine runs, from 0.001 a second at no power to 0.005 at full
Factorio	2016	By throttle	locomotives, cars, and tanks burn chemical fuel; better fuel makes a train accelerate harder and run faster

Every claim about this mechanic, by game (4)

Star Control II 1992	While the flagship moves in HyperSpace, `MoveSIS` adds up how far the flagship moves on each axis (as absolute values) since it entered (`LoadHyperspace` zeroes the sums), takes the square root of the sum of their squares, and charges 1 unit of `FuelOnBoard` for each 16 logical units of that distance; the first charge comes at 32, since the count starts at 1 (computed). The fuel gauge shows `FuelOnBoard` divided by 100 (`FUEL_TANK_SCALE`), so each charge is 1/100 of a shown unit. Nothing is charged with an empty tank or while the `ARILOU_SPACE_SIDE` game state is above 1. The atlas reads those values as QuasiSpace: hyper.c loads the `ARISPACE` graphics into `hyperstars[2]`, picks the stars as `hyperstars[1 + (ARILOU_SPACE_SIDE >> 1)]`, and from 2 up `AddEncounterElement` returns at once, adding no encounter.	Code
Pilotwings 64 1996	In the US version of Pilotwings 64, the gyrocopter's fuel is a number from 0 to 1, starting at the value the task's first start pad holds, or 0 if the task has no start pad (`db_getstart`). While `usingFuel` is set, `func_80307EA8` takes off each update the frame time times a rate read from a curve of the power (`unkB4`, the throttle that A raises and B lowers, which the HUD shows as power; in the throttle's case 0 A sets `usingFuel`, and in cases 1 and 2 A sets it only with fuel above 0): 0.001 at 0, 0.002 at 0.5, and 0.005 at full, linear between. The frame time (`D_8034F854`) is the time since the last frame held between 0.01 and 0.1, so the rate is per second, and a full tank lasts 200 s at full power and 1,000 s at none (computed). At 0 it clears `usingFuel`. In a Class B task, each update that `func_802E08F4` returns nonzero for the craft's position sets the fuel to 1, and `SFX_UI_FUEL_ADDED` plays on the first. `func_80307EA8` does none of this, refill or drain, while `unkC1` is set or in state 2 (`unkC0`). Separately, the HUD update in code_7CF30.c warns below 0.15 (`TEXT_FUEL_WAR`) and at 0 (`TEXT_FUEL_OUT`).	Code
Factorio 2016	A locomotive burns chemical fuel (wood, coal, solid fuel, rocket fuel, nuclear fuel) from three fuel slots.	Code
Factorio 2016	Better fuels make a locomotive accelerate faster and run faster: solid fuel gives ×1.2 acceleration and ×1.05 top speed, rocket fuel ×1.8 and ×1.15, and nuclear fuel ×2.5 and ×1.15. Wood (2 MJ) and coal (4 MJ) set neither.	Code

References

^ a b cIn the US version of Pilotwings 64, the gyrocopter's fuel is a number from 0 to 1, starting at the value the task's first start pad holds, or 0 if the task has no start pad (db_getstart). While usingFuel is set, func_80307EA8 takes off each update the frame time times a rate read from a curve of the power (unkB4, the throttle that A raises and B lowers, which the HUD shows as power; in the throttle's case 0 A sets usingFuel, and in cases 1 and 2 A sets it only with fuel above 0): 0.001 at 0, 0.002 at 0.5, and 0.005 at full, linear between. The frame time (D_8034F854) is the time since the last frame held between 0.01 and 0.1, so the rate is per second, and a full tank lasts 200 s at full power and 1,000 s at none (computed). At 0 it clears usingFuel. In a Class B task, each update that func_802E08F4 returns nonzero for the craft's position sets the fuel to 1, and SFX_UI_FUEL_ADDED plays on the first. func_80307EA8 does none of this, refill or drain, while unkC1 is set or in state 2 (unkC0). Separately, the HUD update in code_7CF30.c warns below 0.15 (TEXT_FUEL_WAR) and at 0 (TEXT_FUEL_OUT).Coden64decomp/pw64revised

How we know

85    D_803694D0.count = 3;
86    D_803694D0.unk4[0].x = 0.0f, D_803694D0.unk4[0].y = 0.001f;
87    D_803694D0.unk4[1].x = 0.5f, D_803694D0.unk4[1].y = 0.002f;
88    D_803694D0.unk4[2].x = 1.f, D_803694D0.unk4[2].y = 0.005f;

src/app/gyrocopter.c lines 84–88 at cb66cb2 · upstream ↗

1454void func_80307EA8(GyrocopterData* gcData) {
⋮
1460    if ((gcData->unkC1 != 0) || (gcData->unkC0 == 2)) {
⋮
1462        return;
⋮
1464    if (D_8036957E == CLASS_B) {
1465        if (func_802E08F4(gcData->unk10.m[3][0], gcData->unk10.m[3][1], gcData->unk10.m[3][2]) != 0) {
1466            if (gcData->unk67E == 0) {
1467                gcData->unk67E = 1;
1468                sndPlaySfx(SFX_UI_FUEL_ADDED);
⋮
1473            gcData->fuel = 1.0f;
⋮
1478    if ((gcData->fuel > 0.0f) && gcData->usingFuel) {
1479        gcData->fuel -= func_80313F08(&D_803694D0, gcData->unkB4) * D_8034F854;
1480        if (gcData->fuel <= 0.0f) {
⋮

src/app/gyrocopter.c lines 1454–1488 at cb66cb2 · upstream ↗

257f32 func_80313F08(Unk803599D0* arg0, f32 arg1) {
⋮
278    temp_fv1 = (arg1 - prev->f[0]) / (cur->f[0] - prev->f[0]);
279    return (cur->f[1] * temp_fv1) + (prev->f[1] * (1.0f - temp_fv1));

src/app/code_9A960.c lines 257–280 at cb66cb2 · upstream ↗

9f32 D_8034F854 = 0.1000000015f; // actual time since last frame

src/app/code_9A960.c line 9 at cb66cb2 · upstream ↗

213    temp_fv0 = uvGfxGetFrameTime();
214    if (temp_fv0 < 0.01f) {
215        D_8034F854 = 0.01f;
216    } else if (temp_fv0 > 0.1f) {
217        D_8034F854 = 0.1f;
218    } else {
219        D_8034F854 = temp_fv0;

src/app/code_9A960.c lines 210–220 at cb66cb2 · upstream ↗

95    db_getstart(&gcData->unk10, &gcData->unk190, &sp5F, &gcData->fuel);

src/app/code_7CF30.c line 95 at cb66cb2 · upstream ↗

260    temp_v1 = taskGetTPAD(&sp44);
261    if (temp_v1 == 0) {
⋮
271        if (fuel != NULL) {
272            *fuel = 0.0f;
⋮
274    } else {
⋮
278        first = &sp44[0];
⋮
292        if (fuel != NULL) {
293            *fuel = first->unk2C;

src/app/code_66F70.c lines 260–294 at cb66cb2 · upstream ↗

248        switch (gcData->unk5F) {
249        case 0:
250            if (buttons & A_BUTTON) {
251                gcData->unkB0 += gcData->unk654 * D_8034F854;
252                if (!gcData->usingFuel) {
253                    gcData->usingFuel = TRUE;
⋮
256            if (buttons & B_BUTTON) {
257                gcData->unkB0 -= gcData->unk658 * D_8034F854;
⋮
274        case 2:
⋮
279                if (buttons & A_BUTTON) {
280                    gcData->unkB0 += gcData->unk648 * D_8034F854;
281                    if (!gcData->usingFuel && (gcData->fuel > 0.0f)) {
⋮

src/app/code_7CF30.c lines 248–309 at cb66cb2 · upstream ↗

473            if (hud->fuel > 0.0f) {
474                hud->power = gcData->unkB4;

src/app/code_7CF30.c lines 473–474 at cb66cb2 · upstream ↗

494                if ((gcData->fuel <= 0.0f) && !gcData->fuelEmpty) {
495                    hudWarningText(TEXT_FUEL_OUT, 1.5f, 8.0f);
⋮
497                } else if ((gcData->fuel < 0.15f) && !gcData->hasLowFuel) {
498                    hudWarningText(TEXT_FUEL_WAR, 1.5f, 8.0f);

src/app/code_7CF30.c lines 494–499 at cb66cb2 · upstream ↗

Checked against the evidence by its author, an AI model, 2026-10-22.

Revised after a check by a second AI model, 2026-10-22.

In the claim ledger

^ a b c dWhile the flagship moves in HyperSpace, MoveSIS adds up how far the flagship moves on each axis (as absolute values) since it entered (LoadHyperspace zeroes the sums), takes the square root of the sum of their squares, and charges 1 unit of FuelOnBoard for each 16 logical units of that distance; the first charge comes at 32, since the count starts at 1 (computed). The fuel gauge shows FuelOnBoard divided by 100 (FUEL_TANK_SCALE), so each charge is 1/100 of a shown unit. Nothing is charged with an empty tank or while the ARILOU_SPACE_SIDE game state is above 1. The atlas reads those values as QuasiSpace: hyper.c loads the ARISPACE graphics into hyperstars[2], picks the stars as hyperstars[1 + (ARILOU_SPACE_SIDE >> 1)], and from 2 up AddEncounterElement returns at once, adding no encounter.CodeThe Ur-Quan Masters (2002 import)revised
How we know
```
91	if (GLOBAL_SIS (FuelOnBoard)
92			&& GET_GAME_STATE (ARILOU_SPACE_SIDE) <= 1)
⋮
99		hyper_dx += new_dx;
⋮
102		hyper_dy += new_dy;
⋮
104		hyper_dist = square_root (
105				(DWORD)hyper_dx * hyper_dx
106				+ (DWORD)hyper_dy * hyper_dy
⋮
108		cur_fuel_ticks = hyper_dist >> 4;
109		if (cur_fuel_ticks > (COUNT)fuel_ticks)
⋮
112			DeltaSISGauges (0, fuel_ticks - cur_fuel_ticks, 0);
⋮
121			fuel_ticks = (BYTE)cur_fuel_ticks;
```
sc2/src/sc2code/hyper.c lines 91–122 at 2f5b2c3 · upstream ↗
```
296	if ((dx || dy) && LOBYTE (GLOBAL (CurrentActivity)) == IN_HYPERSPACE)
297		MoveSIS (&dx, &dy);
```
sc2/src/sc2code/process.c lines 296–297 at 2f5b2c3 · upstream ↗
```
298	hyper_dx = hyper_dy = 0;
299	fuel_ticks = 1;
```
sc2/src/sc2code/hyper.c lines 298–299 at 2f5b2c3 · upstream ↗
```
645	if (fuel_delta != 0)
⋮
651		else
⋮
656					GLOBAL_SIS (FuelOnBoard) / FUEL_TANK_SCALE
⋮
661			else if ((GLOBAL_SIS (FuelOnBoard) += fuel_delta) >
⋮
667				GLOBAL_SIS (FuelOnBoard) / FUEL_TANK_SCALE
⋮
671			wsprintf (buf, "%u", new_coarse_fuel);
```
sc2/src/sc2code/sis.c lines 645–671 at 2f5b2c3 · upstream ↗
```
75#define FUEL_TANK_SCALE 100
```
sc2/src/sc2code/sis.h line 75 at 2f5b2c3 · upstream ↗
```
288		hyperstars[2] = CaptureDrawable (
289				LoadGraphic (ARISPACE_MASK_PMAP_ANIM)
```
sc2/src/sc2code/hyper.c lines 288–289 at 2f5b2c3 · upstream ↗
```
764		HyperSpaceElementPtr->current.image.farray =
765				&hyperstars[1 + (GET_GAME_STATE (ARILOU_SPACE_SIDE) >> 1)];
```
sc2/src/sc2code/hyper.c lines 764–765 at 2f5b2c3 · upstream ↗
```
893AddEncounterElement (ENCOUNTERPTR EncounterPtr,
⋮
901	if (GET_GAME_STATE (ARILOU_SPACE_SIDE) >= 2)
902		return (0);
```
sc2/src/sc2code/hyper.c lines 893–902 at 2f5b2c3 · upstream ↗
Checked against the evidence by its author, an AI model, 2026-10-22.
Revised after a check by a second AI model, 2026-10-22.
In the claim ledger

Sources

Code

Smith, Garrett and pw64 contributors. 2026. “pw64: a decompilation of Pilotwings 64 (n64decomp/pw64).” Commit cb66cb2. n64decomp/pw64 @ cb66cb2 · licence, all uses
Reiche, Paul, Fred Ford, and The Ur-Quan Masters project. 2002. “The Ur-Quan Masters: Star Control II's 3DO source, the project's initial import.” Commit 2f5b2c3. sc2/uqm @ 2f5b2c3 · licence, all uses

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