Bevy Educational (thin router)

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

When to use

Load this for prompts, answers, and progress flags.

ECS shape

• Components hold a prompt and each choice as plain data.
• Resources hold how many answers were graded and how many were correct.
• Systems select a choice, then grade it. .chain() keeps the grade after the selection.
• Schedule: gameplay mode changes go through bevy-state-machines.

[package]
name = "educational"
version = "0.1.0"
edition = "2021"

[dependencies]
bevy = "0.20"

One prompt, two choices, one progress resource.

#[derive(Component)]
struct Prompt {
    text: String,
}

#[derive(Component)]
struct Choice {
    label: String,
    correct: bool,
    picked: bool,
    graded: bool,
}

#[derive(Resource, Default)]
struct LessonProgress {
    answered: u32,
    correct: u32,
}

fn spawn_lesson(mut commands: Commands) {
    commands.spawn(Prompt {
        text: "Which way is north?".to_string(),
    });
    commands.spawn(Choice {
        label: "Up".to_string(),
        correct: true,
        picked: false,
        graded: false,
    });
    commands.spawn(Choice {
        label: "Down".to_string(),
        correct: false,
        picked: false,
        graded: false,
    });
    commands.init_resource::<LessonProgress>();
}

fn pick_first(mut choices: Query<&mut Choice>) {
    for mut choice in &mut choices {
        if choice.correct && !choice.graded && !choice.picked {
            choice.picked = true;
            break;
        }
    }
}

fn grade(mut progress: ResMut<LessonProgress>, mut choices: Query<&mut Choice>) {
    for mut choice in &mut choices {
        if choice.picked && !choice.graded {
            progress.answered = progress.answered.saturating_add(1);
            if choice.correct {
                progress.correct = progress.correct.saturating_add(1);
            }
            choice.graded = true;
            choice.picked = false;
        }
    }
}

pub struct LessonPlugin;

impl Plugin for LessonPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, spawn_lesson)
            .add_systems(Update, (pick_first, grade).chain());
    }
}

pick_first and grade both write Choice, so they stay chained.

A readout only reads progress.

#[derive(Resource, Default)]
struct LessonProgress {
    answered: u32,
    correct: u32,
}

fn show_score(progress: Res<LessonProgress>) {
    let _answered = progress.answered;
    let _correct = progress.correct;
}

pub struct ScorePlugin;

impl Plugin for ScorePlugin {
    fn build(&self, app: &mut App) {
        app.init_resource::<LessonProgress>()
            .add_systems(Update, show_score);
    }
}

Lesson data

Routing

• bevy-ui-text - Prompts.
• bevy-ui-layout - Choices.
• bevy-save-load - Progress saves.
• bevy-state-machines - Lesson mode.

Scope

• Prompts, choices, and the progress resource are gameplay data you define. UI text and layout stay on the linked UI skills.

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.

• No scene-tree types in Bevy code. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• 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 links stay on the unversioned learn pages.

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

• bevy-ui-text - Prompts.
• bevy-ui-layout - Choices.
• bevy-save-load - Progress saves.
• bevy-state-machines - Lesson mode.

Downstream / consumers

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

Master

• bevy-master - Bevy router.