ferravexBuild game loops from small rules
Use ferravex_play::gameplay or ferravex_engine::gameplay. All systems use first-party Rust and std, independent of rendering/ECS/platform services. Configure rules at setup, advance them using the simulation clock, and apply their accepted results through the host's authority. Constructors validate limits; invalid runtime input preserves state. LoopError distinguishes invalid data, exhausted capacity and unavailable actions.
Start with a runnable recipe
cargo run -p ferravex-play --example gameplay_recipe --offline --lockedThe example takes a six-enemy, two-wave specification, produces XP and upgrades, awards wave materials, then crafts a reward after a workbench interaction. Its tiny headless host immediately confirms defeats to show composition; replace that part with actual actors and collision. The three game integrations demonstrate actual physics and controls.
Pick rules for the game
| Need | API | Host responsibility |
|---|---|---|
| Forgiving actions | buffer::CommandBuffer<T> | Push press edges; consume only when executable |
| Chained rewards | combo::ScoreChain | Supply accepted, deduplicated events; break on damage/misses |
| Earned progression | progression::Progression | Apply returned promotions once |
| Varied loot | loot::{RewardTable<N>,RewardRng} | Own seed and stable reward IDs |
| Bounded reward droughts | pity::PityCounter | Count eligible events only |
| Pickup attraction | pickup::Magnet | Resolve walls and accepted collection |
| Items and currencies | inventory::Inventory<N> | Define item IDs and consistent stack limits |
| Crafting | crafting::craft | Supply trusted recipe prices, outputs and permissions |
| Roguelike builds | upgrades::Upgrades<N> | Spend earned points and define rank effects |
| Reload rhythm | magazine::Magazine | Commit damage only when a shot is accepted |
| Heavy attacks | charge::ChargeAction | Supply holds/releases; commit costs on returned releases |
| Homing | homing::steer | Supply a perceived/authorized target and run collision |
| Piercing and ricochets | projectile::ProjectileBudget<N> | Confirm hits and use generational target IDs |
| Safe spawning | spawn::SpawnSelector | Check world occupancy before admitting a spawn |
| Wave arcs | waves::WaveSequence<N> | Track actual live actors; apply clear rewards once |
| Hold interactions | interaction::Interaction | Validate range, visibility, permissions and button state |
| Stagger openings | stagger::Stagger | Apply allowed interruption and movement restrictions |
| Escape/recovery | shield::Shield | Apply returned unabsorbed damage to health |
| Respawn routes | checkpoint::Checkpoints<T,N> | Validate anchor geometry and restore world/save state |
| Timed challenges | trial::Trial<N> | Trigger ordered splits from actual route crossings |
| Springboards | platforms::LaunchPad | Supply real landings; apply returned speed |
| Temporary terrain | platforms::CrumblePlatform | Exclude absent surfaces from collision |
| Skill rewards | skill::PrecisionReturns | Supply accepted normalized returns and intervening progress |
N-sized inventories, tables, histories, upgrades and routes use fixed storage and explicit capacity limits. No system queries hidden world state or performs network I/O. Keep rule IDs/seeds with saved runs. Checkpoint snapshots restore an anchor, not an entire level; use the existing typed save/objective systems for world state. Floating-point simulation is not a promise of cross-platform bitwise determinism.
Actual game hosts
Neon Swarm combines safe spawn selection, abilities, telegraphed attacks, poise, shields, magazines, XP, upgrades, pickups and score chains. Its versioned record context separates the changed rules from earlier runs.
Emberline combines the existing swept character motor with collectible chains, ordered time-trial splits, inventory-earned air jumps, contact-driven springboards, crumbling bonus terrain and ordered checkpoint anchors. Original ground jump forgiveness remains in the character motor.
Orbit Breaker combines continuous ball casts with volley chains, seeded/pity drops, magnetic pickup motion, a limited opening rescue, charged serves and gated precision returns. Empty bounces cannot farm precision rewards.
Run each game's tests to exercise ordinary-input victory, loss/reset and focused new-mechanic regressions. docs/GAMEPLAY_40.md records the delivery series.