Bevy Roguelike (thin router)

Genre router. Domain work lives in the Bevy skills below.

When to use

Load this for run seeds, room generation, and permadeath flags.

ECS shape

• Components hold the genre's per-entity flags as plain data. This file does not name new engine types.
• Resources hold run-wide counters (score, wave index, seed) via bevy-data-resources.
• Systems read those components on Update or the fixed timestep from bevy-master. Order them with .chain() when a later system must see the result.
• Schedule: gameplay mode changes go through bevy-state-machines. Do not invent a genre plugin.

Routing

• bevy-procedural-generation - Seed and spawn.
• bevy-turn-system - Turn order when the run is turn-based.
• bevy-inventory-system - Run loot.
• bevy-rpg-stats - Run stats.

Examples

[dependencies]
bevy = "0.20"
rand = "0.9"

The run seed is one resource. Rooms are entities. StdRng is built inside the system so the seed stays on the resource.

use rand::rngs::StdRng;
use rand::{Rng, SeedableRng};

#[derive(Resource)]
struct RunSeed(u64);

#[derive(Component)]
struct Room {
    x: i32,
    y: i32,
}

fn carve(mut commands: Commands, seed: Res<RunSeed>) {
    let mut rng = StdRng::seed_from_u64(seed.0);
    for _ in 0..8 {
        commands.spawn(Room {
            x: rng.random_range(-6..6),
            y: rng.random_range(-6..6),
        });
    }
}

fn install_run(app: &mut App) {
    app.insert_resource(RunSeed(0x5EED))
        .add_systems(Startup, carve);
}

Permadeath is a flag on the actor plus a run-wide resource. One system writes both.

#[derive(Component)]
struct Actor {
    hp: i32,
}

#[derive(Resource)]
struct RunOver(bool);

fn permadeath(mut actors: Query<&mut Actor>, mut over: ResMut<RunOver>) {
    for mut actor in &mut actors {
        if actor.hp > 0 {
            continue;
        }
        actor.hp = 0;
        over.0 = true;
    }
}

Turn energy accumulates on a resource. Acting spends it. Chain the two systems because both write TurnClock.

#[derive(Resource)]
struct TurnClock {
    energy: f32,
}

fn charge(time: Res<Time>, mut clock: ResMut<TurnClock>) {
    clock.energy = (clock.energy + time.delta_secs()).min(1.0);
}

#[derive(Component)]
struct Actor {
    hp: i32,
}

fn spend(mut clock: ResMut<TurnClock>, mut actors: Query<&mut Actor>) {
    if clock.energy < 1.0 {
        return;
    }
    clock.energy = 0.0;
    for mut actor in &mut actors {
        if actor.hp > 0 {
            actor.hp -= 1;
        }
    }
}

fn install_turns(app: &mut App) {
    app.insert_resource(TurnClock { energy: 0.0 })
        .add_systems(Update, (charge, spend).chain());
}

Loot on the floor is an entity the actor can pick up by grid distance.

#[derive(Component)]
struct Loot {
    value: u32,
}

#[derive(Component)]
struct GridPos {
    x: i32,
    y: i32,
}

#[derive(Component)]
struct Actor;

#[derive(Resource)]
struct RunSeed(u64);

fn pickup(
    mut commands: Commands,
    actors: Query<&GridPos, With<Actor>>,
    loot: Query<(Entity, &GridPos, &Loot)>,
    mut wallet: ResMut<RunSeed>,
) {
    for actor in &actors {
        for (entity, pos, item) in &loot {
            if actor.x == pos.x && actor.y == pos.y {
                wallet.0 = wallet.0.wrapping_add(u64::from(item.value));
                commands.entity(entity).despawn();
            }
        }
    }
}

RunSeed in pickup is only a stand-in counter so the example stays inside one resource. A coin wallet belongs on bevy-economy-system. permadeath and spend both write Actor; chain them when both run.

Scope

• Noise and larger maps route to bevy-procedural-generation.
• Inventory stacks route to bevy-inventory-system.

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

Load references/ecs-ownership.md for the ownership table.

NEVER

• Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.

• Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.

• Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.

• Do not rebuild StdRng from a new seed each frame. WHY: the run seed stays on RunSeed so room layout stays reproducible.

• Do not let permadeath and spend both write Actor without .chain(). WHY: unordered mutable queries on the same component conflict.

• No invented genre APIs. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• Do not pick a physics or net crate here. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

The library pin on bevy-master stays 0.20.0. Official pages stay on the unversioned latest branch.

Official Documentation

• Assets - Official asset catalog. No third-party crate was selected.
• Examples - Example tree on the latest branch.
• ECS - Component, systems, Query, Startup, Update, and .chain().
• Plugins - Plugin, DefaultPlugins, MinimalPlugins, and add_plugins.

Related Skills

Prerequisites

• bevy-master - ECS ownership and schedules.
• bevy-ecs-composition - Spawn and query shape.

Complements

• godot-genre-roguelike - Roguelike on the Godot engine, same depth.
• bevy-procedural-generation - Seed and spawn.
• bevy-turn-system - Turn order when the run is turn-based.
• bevy-inventory-system - Run loot.
• bevy-rpg-stats - Run stats.

Downstream / consumers

• None. This router does not own a second implementation.

Master

• bevy-master - Bevy router.