What it does
These rules plug into a cave-flyer session, which already owns the ship, its gun, shield and beam, the guns that
shoot back, doors and lives. The reactor rule reads a planet's reactor. Each hit adds damage and stuns the guns for a
while; bases marked as gated hold their fire while the reactor is stunned or counting down. Past a critical level a
countdown starts, and at zero the planet blows up with everything on it. A crash while the reactor is critical ends
the planet as destroyed, with no bonus and angrier guns on the next mission.
The pod rule reads a planet's pod and its checkpoints. The ship hovers over the pod's stand with the beam on, then
pulls away to tether it, on a rigid rod or a rope from thrust-craft, so the heavy pod swings the ship about the
pair's centre. Towing it up through the orbit line pays the mission bonus, more if the reactor is critical; leaving
without it costs a ship and flies the planet again. After a crash the ship restarts at the checkpoint above where it
died, or, carrying the pod, at the one at or below it with the pod still attached.
thrustPreset assembles a whole game: the six planets traced from the original's level tables (walls, guns and
their firing arcs, fuel, the reactor, the pod, switches, doors and checkpoints), the original's gravity per planet,
damping, rotation, bullets, fuel use, gun behaviour, reactor damage and countdown, scoring and extra ships, and four
passes: normal, reversed gravity, an invisible landscape, and both.
Features
- The reactor rule — damage per hit, stunned guns, a countdown from a critical level, and a planet destroyed at zero.
- Gated guns — bases that hold fire while the reactor is stunned or counting down.
- The pod rule — arm the beam over the stand, pull away to tether, tow through the orbit line for the bonus.
- Rod or rope — a rigid rod as in the original, or a rope, with a configurable pod mass.
- Checkpoints — restarts above the crash, or at or below it when carrying the pod.
- Rules that stand alone — use only the pod, only the reactor, or both.
- A six-planet preset — traced planets, the original's tables and four passes.
- Pieces to reuse — the planets, a gun-arc converter, the gravity table and the ship outline.
Good for
- Cave-flying games with a pod to tow out, in the style of Thrust on the BBC Micro.
- Sabotage missions, where blowing a reactor and escaping before the countdown ends is the goal.
- Rescue games that tether a heavy load and fly it out of a cavern.
- Your own cave flyer with a single borrowed objective, such as a pod to rescue on a tile-mask cave.
Make it yours
The pack factory has no options; the rules take theirs. reactorRule takes the damage per hit and its random extra,
the critical level, the stun per point of damage and at the start, and the countdown and its step. podRule takes the
bonus: the points per planet, an offset and an extra when the reactor is critical. The arming distance, the pull that
tethers and whether it is a rod or a rope are set on the ship's tractor.
thrustPreset takes the difficulty (Easy and Normal slow the guns and add fuel and ships; Arcade follows the
original), a seed, a gun-rate multiplier, a gravity multiplier, lives, starting fuel, the pod's mass, rod or rope,
and which planets to play in what order. Two different uses: the full six-planet game on Arcade with a rod; and a
cave game of your own design that adds only podRule to its rules, with a rope and a pod three times the ship's
mass.
A quick look
The preset in a cave-flyer session, or the pod rule alone in a game of your own:
const CF = game.caveFlyer, TR = game.thrustRules;
const g = CF.createCaveFlyer(TR.thrustPreset({ difficulty: 'normal', tether: 'rope', planets: [0, 1, 2] }));
// or a game of your own with only the pod:
const def = { ...myCave, rules: [TR.podRule({ bonus: { per: 100, offset: 1, destroyed: 0 } })] };
TR.podOf(g.state)?.pod; // 'stand' | 'towed' | 'lost' | 'none'
TR.reactorOf(g.state); // { damage, stun, countdown, countT, alive, present }
Works with
cave-flyer— required: the session these rules plug into.thrust-craft— the flight model, beam and tethers underneath.oids-rescue— for rescuing walkers from factories and docking with a mothership instead.
Good to know
- One pod per planet, and bullets do not hit the towed pod.
- The preset runs at 60 steps a second rather than the original's slower tick, so its motion is smoother but the same on average.
- The pod is a thrust-craft rod with equal masses rather than the original's angle tables, and collisions are geometric rather than pixel tests.
- The shield protects whenever it is held.






