Philosophy

Design principles for playmate.

Building Blocks, Not Frameworks

Playmate provides primitives. Users compose them.

• State machines that can drive anything (animation, AI, gameplay)
• Controllers that work with any physics backend
• Generators that output data, not side effects

We don't dictate game structure. We provide the Lego bricks.

Kinematic Over Dynamic

For character controllers, kinematic beats dynamic:

Approach	Pros	Cons
Kinematic	Predictable, code-driven, "feels right"	You calculate movement yourself
Dynamic	Physically accurate	Floaty, hard to tune, unpredictable

Use physics engines (Rapier) for collision detection. Use code for movement feel.

Warframe-style movement (bullet jumping, aim gliding, wall running) is impossible with dynamic bodies. It's pure kinematic - every velocity vector calculated explicitly.

Hot-Reloadable Feel

Iteration speed matters. You can't feel a game by reading code.

The Setup:

• Logic (Rust): FSMs, vector math, state transitions
• Parameters (Assets): movement.ron - jump_force, slide_decay, gravity
• Bridge: Hot-reload config on save

The Workflow:

1. Write the logic once
2. Run the game
3. Tweak bullet_jump_force from 10.0 to 50.0
4. Instantly feel the difference

No recompile. No restart. Immediate feedback.

State Machines for Behavior

LLMs excel at generating clean FSMs. So do humans. They're explicit, debuggable, composable.

enum MovementState {
    Idle,
    Run,
    Slide,
    BulletJump,
    WallRun,
}

Each state owns its behavior. Transitions are explicit. Edge cases are visible.

Bad: "Can I double jump after a wall hop but not after a bullet jump?" → Hidden in spaghetti logic

Good: State machine with explicit can_double_jump per state → Visible, testable, debuggable

Engine Agnostic

No engine dependencies in core playmate crates.

• Use glam for math (shared by Bevy, macroquad, rend3, others)
• Use serde for serialization (works everywhere)
• Integration crates (e.g., playmate-bevy) provide engine-specific adapters

Playmate works with any Rust game engine or no engine at all.

General Internal, Constrained APIs

Store the general representation, expose simpler APIs for common cases.

Internal complexity, external simplicity. Power users can access the general form.