Bevy 2D physics

When to use

Load this when a Bevy app needs simulated 2D bodies, triggers, or layer filtering before choosing a solver. Pair with bevy-character-movement for player motion that should not be a rigid body. Pair with bevy-spatial-queries for casts that also wait on a solver.

ECS shape

• Components would own body kind, velocity, and collider data once a solver crate is chosen. The ECS page only shows plain Component structs. It does not define a rigid body.
• Resources would own gravity and solver settings. Check the solver docs before naming those fields.
• Systems would step the solver on a fixed schedule. bevy::time documents Fixed and run_fixed_main_schedule (FixedMain). That is a clock, not a physics engine.
• Schedule: fixed timestep for the step; .chain() when a system must see the step result before it runs (ECS page).

Coming from Godot

Godot idea	Bevy idiom
Simulated 2D prop	Entity plus solver-defined components, after a crate is verified
Player locomotion	Not a rigid body. Use bevy-character-movement
Trigger volumes	Choose a physics solver before adding trigger volumes.
Layers and masks	Unverified. Do not copy Godot bit names

Scope

• The bevy 0.20.0 crate feature list on docs.rs has no physics-engine feature. 2D collision shapes, layers, and masks are not Bevy names on these pages.
• Third-party plugins are allowed by the plugins page (add a crate, then add_plugins). Check a 2D physics crate's own docs before naming its plugin path.
• Raycasts, CCD, and collision events need a chosen solver. Route query design to bevy-spatial-queries.

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 2D physics node or server types. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No Avian, Rapier, or any other named physics crate as the chosen solver. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

• No invented collider, layer, or joint APIs. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

docs.rs links use the unversioned latest permalink. The library pin on bevy-master stays 0.20.0.

Official Documentation

• Migration guides - Unversioned hop index.
• bevy crate - Unversioned API index. The 0.20.0 feature list has no physics-engine feature.
• Assets - Official asset catalog. No physics plugin is named from it here.
• Examples - Example tree on the latest branch.
• Quick Start: plugins - Plugin, DefaultPlugins, MinimalPlugins, and third-party add_plugins.
• ECS - Component, systems, Query, Startup, Update, and .chain().
• bevy::time - Fixed and run_fixed_main_schedule (FixedMain) as a clock, not a solver.

Related Skills

Prerequisites

• bevy-master - ECS ownership and the fixed-timestep schedule names.

Complements

• bevy-physics-3d - Simulated 3D bodies and solver choice.
• bevy-character-movement - Player locomotion that should not be a rigid body.
• bevy-spatial-queries - Casts and overlaps. Choose a physics solver before adding them.
• godot-2d-physics - Equivalent Godot skill.

Downstream / consumers

• Combat and shooter skills cover hit detection and shots.

Master

• bevy-master - Bevy router.