# Chain

> Connection kind `chain` (category `mech`, DSL name `chain`, API v1)

Toothed loop coupling two sprockets of the same pitch. Non-slipping — driven sprocket ratios by tooth count (not diameter).

## Accepted ports

- `sprocket.axis` → `sprocket.axis`

## Parameters

- **`side`** — Direction from anchor to driven sprocket in the anchor XY plane. One of right, left, up, down, or { angleDeg: N }.
- **`distance`** — Center-to-center distance between the two sprockets (mm). Defaults to the sum of the two pitch radii × 4.

## Parameters schema

| Parameter | Type | Default | Constraints |
| --- | --- | --- | --- |
| `side` | any | right | allowed: right, left, up, down |
| `distance` | Number | null |  |

## Kinematics

ω_to = ω_from · (teeth_from / teeth_to). Direction is preserved — a chain never crosses.

## Layout

This connection computes the driven component position from the anchor.

## Example

```
connect S1.axis -> S2.axis with mech.chain {
  side: "right"
  distance: 180
}
```