Bevy Mechanic Secrets Agent Skill

Bevy secrets mechanic

When to use

Load this when the player uncovers optional flags that must persist.

ECS shape

• Components: a secret id and a found-set resource you define.
• Resources: run-wide tables live in a resource (bevy-data-resources), not an autoload.
• Systems: mutate those components on Update or the fixed timestep. Use .chain() when damage must land before death.
• Messages: one-shot facts (hit, pickup, quest advance) go through bevy-events-messaging. This file does not add a new event type name.

Coming from Godot

| Godot idea | Bevy idiom |

| --- | --- |

| Secret id | A component on the world object. |

| Found set | A resource of ids. |

| Persist | Hand the set to bevy-save-load. |

Scope

Secret ids, a discovered set, look-at checks, and timed input sequences are components and resources you own. Persistence of that set belongs on bevy-save-load.

Examples

[dependencies]
bevy = "0.20"
serde = { version = "1", features = ["derive"] }

Discovering a secret inserts its id once. A later system can hand Discovered to the save skill.

use serde::{Deserialize, Serialize};
use std::collections::HashSet;

#[derive(Component)]
struct Secret {
    id: u32,
    radius: f32,
}

#[derive(Component)]
struct Seeker;

#[derive(Resource, Default, Serialize, Deserialize)]
struct Discovered {
    ids: HashSet<u32>,
}

fn discover(
    seekers: Query<&Transform, With<Seeker>>,
    secrets: Query<(&Transform, &Secret)>,
    mut found: ResMut<Discovered>,
) {
    for seeker in &seekers {
        for (tf, secret) in &secrets {
            if seeker.translation.distance(tf.translation) <= secret.radius {
                found.ids.insert(secret.id);
            }
        }
    }
}

fn look_at_secret(
    seekers: Query<&Transform, With<Seeker>>,
    secrets: Query<(&Transform, &Secret)>,
    mut found: ResMut<Discovered>,
) {
    for seeker in &seekers {
        let forward = seeker.forward().as_vec3();
        for (tf, secret) in &secrets {
            let to = tf.translation - seeker.translation;
            let dist = to.length();
            if dist < 0.001 || dist > 6.0 {
                continue;
            }
            if (to / dist).dot(forward) > 0.98 {
                found.ids.insert(secret.id);
            }
        }
    }
}

A sequence matcher keeps a rolling window. The classic up-up-down-down-left-right-left-right pattern unlocks when the tail matches before the window expires.

#[derive(Resource)]
struct SequenceSecret {
    pattern: Vec<KeyCode>,
    heard: Vec<KeyCode>,
    time_left: f32,
    window: f32,
    unlocked: bool,
}

impl Default for SequenceSecret {
    fn default() -> Self {
        Self {
            pattern: vec![
                KeyCode::ArrowUp,
                KeyCode::ArrowUp,
                KeyCode::ArrowDown,
                KeyCode::ArrowDown,
                KeyCode::ArrowLeft,
                KeyCode::ArrowRight,
                KeyCode::ArrowLeft,
                KeyCode::ArrowRight,
            ],
            heard: Vec::new(),
            time_left: 0.0,
            window: 2.5,
            unlocked: false,
        }
    }
}

#[derive(Resource, Default)]
struct Discovered {
    ids: std::collections::HashSet<u32>,
}

fn match_sequence(time: Res<Time>, keys: Res<ButtonInput<KeyCode>>, mut seq: ResMut<SequenceSecret>) {
    if seq.unlocked {
        return;
    }
    let dt = time.delta_secs();
    seq.time_left = (seq.time_left - dt).max(0.0);
    if seq.time_left == 0.0 {
        seq.heard.clear();
    }
    let watched = [
        KeyCode::ArrowUp,
        KeyCode::ArrowDown,
        KeyCode::ArrowLeft,
        KeyCode::ArrowRight,
    ];
    for key in watched {
        if keys.just_pressed(key) {
            seq.heard.push(key);
            seq.time_left = seq.window;
        }
    }
    if seq.heard.len() > seq.pattern.len() {
        let extra = seq.heard.len() - seq.pattern.len();
        seq.heard.drain(0..extra);
    }
    if seq.heard == seq.pattern {
        seq.unlocked = true;
        seq.heard.clear();
    }
}

#[derive(Resource)]
struct ProgressUnlock {
    cleared: u32,
    total: u32,
    unlocked: bool,
}

fn unlock_by_progress(mut progress: ResMut<ProgressUnlock>, mut found: ResMut<Discovered>) {
    if progress.unlocked || progress.total == 0 {
        return;
    }
    if progress.cleared * 100 / progress.total >= 80 {
        progress.unlocked = true;
        found.ids.insert(9001);
    }
}

pub struct SecretsPlugin;

impl Plugin for SecretsPlugin {
    fn build(&self, app: &mut App) {
        app.init_resource::<Discovered>()
            .init_resource::<SequenceSecret>()
            .insert_resource(ProgressUnlock {
                cleared: 0,
                total: 10,
                unlocked: false,
            })
            .add_systems(Update, (match_sequence, unlock_by_progress));
    }
}

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

| Piece | Owner | Who may mutate | Schedule |

| --- | --- | --- | --- |

| Data on one entity | Component | One system via Query | Update or FixedMain |

| One value for the whole app | Resource | One system | Startup to insert, then the schedule that reads it |

| Spawn | Commands | The spawning system | Startup for the initial world; later schedules for runtime spawn |

| Order that must not race | .chain() | The chained systems only | Same schedule |

| Plugin boundary | Plugin | build registers systems and resources | Before the app runs |

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

| If you need | Do this | Do not |

| --- | --- | --- |

| Per-entity data | Component + Query | A Godot node script |

| App-wide config or clock | Resource | Copy the value onto every entity |

| Stable simulation step | FixedMain and the Fixed clock | Tie simulation to raw frame Update |

| Startup spawn | Commands in Startup | Spawn from a render system |

| Cross-system notice that is not shared state | Message or observer slot in bevy-events-messaging | A new event type invented in this file |

| An API outside the documented set | Check the official docs first | A made-up crate or API |

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.

• No Godot node, resource, or signal types for this mechanic. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No Godot types in Bevy code. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.
• No invented APIs or unnamed third-party crates as the chosen solver. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

The library pin on bevy-master stays 0.20.0.

Official Documentation

• bevy crate - API reference and Cargo feature list.
• 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 - Hub and schedules.
• bevy-ecs-composition - Components and systems.
• bevy-save-load - Persist flags.
• bevy-data-resources - Tables and definitions.
• bevy-events-messaging - One-shot facts.

Complements

• bevy-state-machines - Mode flags.
• godot-mechanic-secrets - Equivalent Godot skill.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.