Bevy mobile platform

When to use

Load this when targeting touch devices. Store listings and OS permission dialogs stay outside the crate. XR is a separate topic.

ECS shape

• Input: Touches holds active contacts. PinchGesture is a message for two-finger pinch on iOS and macOS.
• Android: enable the android-game-activity feature. android-native-activity is the legacy activity.
• Power: WinitSettings::mobile() waits on input while focused and drops to a one-second wait when unfocused.
• iOS edges: Window::preferred_screen_edges_deferring_system_gestures takes a ScreenEdge.
• Textures: ASTC shows up as TextureFormat::Astc on an Image descriptor after the asset loads.

Examples

[dependencies]
bevy = { version = "0.20", features = ["android-game-activity"] }

Mobile update mode sleeps the loop when the window is backgrounded.

use bevy::winit::WinitSettings;

fn main() {
    App::new()
        .insert_resource(WinitSettings::mobile())
        .add_plugins(DefaultPlugins)
        .run();
}

A stick zone turns the first contact into a unit axis. Keyboard and mouse stay on bevy-input-handling.

#[derive(Component, Default)]
struct MoveIntent {
    axis: Vec2,
}

#[derive(Resource)]
struct StickZone {
    center: Vec2,
    radius: f32,
}

fn read_stick(touches: Res<Touches>, zone: Res<StickZone>, mut intents: Query<&mut MoveIntent>) {
    let Some(touch) = touches.iter().next() else {
        return;
    };
    let offset = touch.position() - zone.center;
    let length = offset.length();
    let axis = if length <= zone.radius && length > 0.0 {
        offset / zone.radius
    } else if length > zone.radius {
        offset / length
    } else {
        Vec2::ZERO
    };
    for mut intent in &mut intents {
        intent.axis = axis;
    }
}

Pinch messages adjust a zoom resource. Registering messages is the engine's job for built-in gesture types.

use bevy::input::gestures::PinchGesture;

#[derive(Resource)]
struct CameraZoom(f32);

fn apply_pinch(mut pinches: MessageReader<PinchGesture>, mut zoom: ResMut<CameraZoom>) {
    for pinch in pinches.read() {
        zoom.0 = (zoom.0 + pinch.0).clamp(0.25, 4.0);
    }
}

Defer system gestures on every screen edge, and count ASTC images already in the asset store.

use bevy::render::render_resource::TextureFormat;
use bevy::window::PrimaryWindow;
use bevy::window::ScreenEdge;

fn defer_system_gestures(mut windows: Query<&mut Window, With<PrimaryWindow>>) {
    let Ok(mut window) = windows.single_mut() else {
        return;
    };
    window.preferred_screen_edges_deferring_system_gestures = ScreenEdge::All;
}

#[derive(Resource, Default)]
struct AstcCount(usize);

fn count_astc(images: Res<Assets<Image>>, mut count: ResMut<AstcCount>) {
    count.0 = images
        .iter()
        .filter(|(_, image)| matches!(image.texture_descriptor.format, TextureFormat::Astc { .. }))
        .count();
}

Same job, Bevy types

Design	Bevy idiom
Touch	Touches on Update
Android activity	android-game-activity Cargo feature
Safe area	ScreenEdge on the primary Window, plus UI padding from bevy-adapt-desktop-to-mobile
Background FPS	WinitSettings::mobile()

Scope

Packaging, signing, and store permission prompts are outside this skill. Touch, pinch, screen edges, ASTC detection, and the mobile update mode are the systems above.

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 scene-tree script hung on 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	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 touch-screen or safe-margin project settings. 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

Official pages stay on unversioned bevy.org URLs. The library pin on bevy-master stays 0.20.0. ScreenEdge is a field on Window. Touch contacts stay on Touches; they are not a separate event struct.

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 - Hub and schedules.
• bevy-ecs-composition - Components and systems.
• bevy-input-handling - Other devices.
• bevy-platform-desktop - Window shell.

Complements

• bevy-adapt-desktop-to-mobile - Layout and input adapt.
• godot-platform-mobile - Equivalent Godot skill.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.