---
title: "Reactor and pod-tow rules: API"
package: "@phaser-ae/thrust-rules"
tier: Pro
version: 3.0.0-1
released: 2026-10-19
updated: 2026-10-20
description: "Two cave-flying objectives as separate rules, a reactor to stun and sabotage and a pod to tow out to orbit, plus a six-planet preset of the 1986 home-computer classic."
url: https://phaser.io/packs/thrust-rules/api
site: Phaser - https://phaser.io
---

# Reactor and pod-tow rules: API

`@phaser-ae/thrust-rules` — Reactor and pod-tow rules for cave-flyer: the reactor's stun and countdown, the pod towed out to orbit, checkpoints, and the Thrust preset's six ROM planets.

## The pack

### `thrustRules`

```ts
function thrustRules(): Pack<{ thrustRules: typeof api }>
```

Install the thrust-rules API (`game.thrustRules`): its rules for cave-flyer and its preset.

## Helpers

### `POD`

```ts
const POD: "pod"
```

The pod's id in the thrust-craft world.

### `podOf`

```ts
function podOf(state: CaveState): PodState | undefined
```

The pod's state in a session, or undefined without `podRule`.

### `podRule`

```ts
function podRule(o: PodOptions = {}): CaveRule
```

Thrust's pod: the objective is to tow it out through the orbit line. The ship needs a beam with a `pod` setting.
While towing, the view follows the middle of the ship and the pod, and the beam cannot take cells.

### `reactorCritical`

```ts
const reactorCritical = (state: CaveState): boolean=> …
```

The reactor is critical: counting down, or blown.

### `reactorOf`

```ts
function reactorOf(state: CaveState): ReactorState | undefined
```

The reactor's state in a session, or undefined without `reactorRule`.

### `reactorRule`

```ts
function reactorRule(o: ReactorOptions): CaveRule
```

Thrust's reactor. Bases marked `gated` hold fire while it is stunned or counting down. A crash while it is critical
ends the planet as destroyed (no bonus, the next mission's guns punished by `gunLevel.destroyed`).

### `THRUST_GRAVITY`

```ts
const THRUST_GRAVITY: number[]
```

Gravity per planet in pixels/s^2: the ROM's `gravity_FRAC` (5, 7, 9, 11, 12, 13)/256 y units per active tick.

### `THRUST_SHIP_OUTLINE`

```ts
const THRUST_SHIP_OUTLINE: Vec2[]
```

Thrust's ship, drawn upright (nose up): an arrowhead with a notched tail.

### `thrustGunCone`

```ts
function thrustGunCone(param: number): { dir: number; spread: number }
```

A gun's fire cone from its `gun_param`: angle index = base + rnd(0..spread mask) + rnd(0..3), 0 up, clockwise.

### `thrustPlanets`

```ts
function thrustPlanets(): CavePlanetDef[]
```

Thrust's planets as cave-flyer planets.

### `thrustPreset`

```ts
function thrustPreset(o: ThrustPresetOptions = {}): CaveFlyerDef
```

Thrust (1986). Easy and Normal change only the guns' fire rate (x0.4, x0.7), the starting fuel (2000, 1500) and the
spare ships (5, 4); Arcade is the ROM: 1000 fuel, three spare ships, an extra ship every 10,000.

## Types

### `PodOptions`

```ts
interface PodOptions
```

The pod rule's options.

- `bonus?: { per: number; offset: number; destroyed: number }` — The mission bonus for towing it out: `per` x (planet index + `offset`), plus `destroyed` if the reactor is critical.

### `PodState`

```ts
interface PodState
```

The pod's state.

- `pod: "stand" | "towed" | "lost" | "none"` — On its stand, towed, lost with the ship, or none on this planet.
- `deathPod: boolean` — It was on the rod when the ship died.

### `ReactorOptions`

```ts
interface ReactorOptions
```

The reactor's numbers (the original's units: damage bytes, seconds converted from its ticks).

- `damage: number` — Damage at the start of each planet.
- `hitRandom: number` — Random damage added per hit: 0 to this.
- `critical: number` — Damage over this starts the countdown.
- `stunPerDamage: number` — The guns stay quiet for the new damage times this many seconds.
- `startStun: number` — Stun at the start of a planet and after a respawn, seconds.
- `countdown: number` — Counts in the countdown.
- `countdownStep: number` — Seconds per count.

### `ReactorState`

```ts
interface ReactorState
```

The reactor's state.

- `damage: number` — Accumulated damage.
- `stun: number` — Seconds the guns stay quiet.
- `countdown: number` — Countdown count, -1 when not critical.
- `countT: number` — Seconds to the next count.
- `alive: boolean` — Still standing.
- `present: boolean` — This planet has a reactor.

### `ThrustPresetOptions`

```ts
interface ThrustPresetOptions
```

Options for `thrustPreset`.

- `difficulty?: CaveDifficulty` — Easy, Normal or Arcade (the ROM's tables). Default 'arcade'.
- `seed?: number` — Seed for gun aim and reactor damage.
- `guns?: number` — Multiply the guns' fire rate. Default from the difficulty.
- `gravity?: number` — Multiply every planet's gravity. Default 1.
- `lives?: number` — Spare ships at the start. Default from the difficulty (3 in the arcade).
- `fuel?: number` — Starting fuel. Default from the difficulty (1000).
- `podMass?: number` — Pod mass relative to the ship. Default 1 (the ROM's midpoint physics: thrust halves when towing).
- `tether?: "rod" | "rope"` — Tow on a rigid rod (the original) or a rope.
- `planets?: number[]` — Which planets, by index 0-5, in play order. Default all six.

---

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