Built-In Physics

Formo ships a full rigid-body physics engine powered by planck.js — a ~40KB Box2D port. No approximations, no tweening hacks. Real forces, real collisions, real contact response.

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One-Click Setup

Add the physics module to any node. Pick a body type. Press play. Gravity pulls at 9.8 m/s² and collisions just work.

3 Body Types

Type	Behavior
Dynamic	Affected by forces, gravity, and collisions. The default for game objects.
Static	Immovable. Walls, floors, platforms. Zero mass, infinite inertia.
Kinematic	Moved by code only. Elevators, moving platforms, scripted obstacles.

Switch between them with the TripleToggle control — one click, no dropdowns.

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Automatic Colliders

The engine reads your shape type and generates the right collider — no manual setup.

Shape	Collider	Notes
Rectangle	Box	Axis-aligned, matches width and height
Ellipse	Circle	Uses the larger radius
Polygon	Convex polygon	Up to 8 vertices, auto-decomposed

Coordinate conversion uses PIXELS_PER_METER = 50. A 100px square becomes a 2m box in the physics world.

Multi-Collider Bodies

One node can hold multiple named colliders with independent type, scale, and offset. Build an L-shaped wall from two box colliders. Give a character a wide foot sensor and a narrow body hitbox. Add and remove colliders in the ColliderGroup panel.

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Material Properties

Every collider exposes 7 tunable properties. Drag the SliderInput controls — pointer-lock gives you infinite drag range.

Property	Range	Default	Effect
density	0 – 100	1.0	Mass per unit area
friction	0 – 1	0.3	Surface grip between bodies
restitution	0 – 1	0.0	Bounciness on impact
gravityScale	-10 – 10	1.0	Per-body gravity multiplier
fixedRotation	bool	false	Prevents angular velocity
fixX	bool	false	Locks horizontal movement
fixY	bool	false	Locks vertical movement

FixToggle buttons lock axes instantly. Position is captured when toggled — no drift.

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Collision Events

The collide event fires on contact with full context.

// event properties
event.target         // the other node
event.normal         // contact normal vector
event.point          // world-space contact point
event.collider       // this node's collider name
event.targetCollider // other node's collider name

Write game logic directly in the handler:

if (event.target.is("brick")) {
  event.target.destroy()
  Score.text = Tag.brick.length
}

Sensor Colliders

Set this.sensor = true on any collider. It detects overlaps but generates no physical response — perfect for triggers, pickups, and damage zones.

Collision Bypass

Call this.disableCollisions(otherNode) to let two specific bodies pass through each other. Re-enable with this.enableCollisions(otherNode).

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Formula Integration

Physics properties are first-class formula targets. Read velocity, apply forces, control movement — all from expressions.

this.velocityX            // read horizontal velocity
this.velocityY            // read vertical velocity
this.applyForce(x, y)    // continuous force (newtons)
this.applyImpulse(x, y)  // instant momentum change

The VelocityWidget shows a direction dial and magnitude — drag to set initial velocity visually before play.

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Nested Physics

Physics works inside transformed containers. The engine resolves parent rotation, scale, and translation before syncing positions — bodies inside a rotated group collide correctly.

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Stable Simulation

The engine uses a fixed-timestep accumulator. Physics steps at a constant rate regardless of frame rate — 60fps or 144fps, the simulation produces identical results. No frame-dependent jitter, no tunneling at low FPS.

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Non-Destructive Play

Press play — the engine snapshots every node’s position, rotation, and velocity. Physics runs. Shapes fly, bounce, collide. Press stop — everything resets to the exact captured state. Iterate without fear.

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Start building

Real physics. Visual controls. Formula-driven logic. Open Formo and drop a ball.

Open Formo →