Bevy Idle clicker (thin router)

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

When to use

Load this for currencies that tick while the app runs.

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-economy-system - Currencies.
• bevy-ui-layout - Click target.
• bevy-input-handling - Click.
• bevy-save-load - Offline progress.

Examples

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

The wallet is one resource. Generators add coins on Update from Time::delta_secs.

#[derive(Resource)]
struct Wallet {
    coins: f64,
    per_second: f64,
}

fn tick_income(time: Res<Time>, mut wallet: ResMut<Wallet>) {
    wallet.coins += wallet.per_second * f64::from(time.delta_secs());
}

fn click(
    mouse: Res<ButtonInput<MouseButton>>,
    mut wallet: ResMut<Wallet>,
) {
    if mouse.just_pressed(MouseButton::Left) {
        wallet.coins += 1.0;
    }
}

fn install_income(app: &mut App) {
    app.insert_resource(Wallet {
        coins: 0.0,
        per_second: 2.5,
    })
    .add_systems(Update, (tick_income, click).chain());
}

Each building is an entity. One system writes the wallet so the generators cannot race each other.

#[derive(Component)]
struct Generator {
    rate: f64,
    owned: u32,
}

#[derive(Resource)]
struct Wallet {
    coins: f64,
    per_second: f64,
}

fn generators_to_wallet(
    gens: Query<&Generator>,
    mut wallet: ResMut<Wallet>,
    time: Res<Time>,
) {
    let mut rate = 0.0;
    for building in &gens {
        rate += building.rate * f64::from(building.owned);
    }
    wallet.per_second = rate;
    wallet.coins += rate * f64::from(time.delta_secs());
}

tick_income and generators_to_wallet both write Wallet. Run only one of them, or .chain() them if a later system must see the sum.

Offline progress stores a unix second, then banks elapsed time the next time the resource is inserted.

use serde::{Deserialize, Serialize};
use std::time::{SystemTime, UNIX_EPOCH};

#[derive(Resource, Clone, Serialize, Deserialize)]
struct IdleClock {
    last_unix: u64,
    per_second: f64,
    banked: f64,
}

fn bank_offline(mut clock: ResMut<IdleClock>) {
    let now = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(clock.last_unix);
    let elapsed = now.saturating_sub(clock.last_unix).min(8 * 60 * 60);
    clock.banked += clock.per_second * elapsed as f64;
    clock.last_unix = now;
}

#[derive(Resource)]
struct Wallet {
    coins: f64,
}

fn claim(mut clock: ResMut<IdleClock>, mut wallet: ResMut<Wallet>) {
    wallet.coins += clock.banked;
    clock.banked = 0.0;
}

bank_offline and claim both mutate IdleClock, so chain them. Persistence of the struct belongs on bevy-save-load.

Scope

• Currencies, the click, and the layout route to the skills in Routing.
• Cap offline time in the resource (the example caps at eight hours) so a bad clock cannot mint unbounded coins.

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 field stored off the entity
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	Use the examples in this skill	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.

• Do not let tick_income and generators_to_wallet both add Wallet.coins unless they are .chain()ed or only one is installed. WHY: unordered systems run in parallel and one income write is dropped.

• Do not leave offline elapsed uncapped. WHY: a clock jump mints unbounded coins into the wallet resource.

• 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-idle-clicker - Idle clicker on the Godot engine, same depth.
• bevy-economy-system - Currencies.
• bevy-ui-layout - Click target.
• bevy-input-handling - Click.
• bevy-save-load - Offline progress.

Downstream / consumers

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

Master

• bevy-master - Bevy router.