# Picture Frame Mount Creator (CAD Engine Specification)

This file provides system information, architecture guidelines, and syntax reference for picture frame matboard design inside the Picture Frame Mount Creator CAD application.

> For the comprehensive technical layout schema, binary bytecode specifications, vector plotter details, and exporter mathematics, see the [Full Technical Specification](/llms-full.txt).

---

## 1. System Overview

- **Application Name**: Picture Frame Mount Creator & Matboard Designer
- **Domain**: Custom Bespoke Framing Web CAD
- **Client Frame Space Coordinates**:
  - Center of the matboard is absolute `(0, 0)`.
  - Apertures are positioned with `(x, y)` relative offsets from the matboard center.
  - Supported unit types: Millimeters (`mm`), Centimeters (`cm`), and Inches (`in`).
  - Standard physical sizes are calculated dynamically based on margins or absolute selections.

---

## 2. Lisp S-Expression CAD Console (JSON-HC)

To make CAD layouts extremely compact for LLMs and conversational interfaces, we serialize matboard layouts into highly dense Lisp-style S-Expressions.

### S-Expression EBNF Grammar Reference
```ebnf
layout     ::= '(' 'layout' unit width height layers reveal1 reveal2 color1 color2 color3 core margins? bed? dxf-cut? apertures ')'
unit       ::= '(' 'unit' ('mm' | 'cm' | 'in') ')'
width      ::= '(' 'width' float ')'
height     ::= '(' 'height' float ')'
layers     ::= '(' 'layers' (1 | 2 | 3) ')'
reveal1    ::= '(' 'reveal1' float ')'
reveal2    ::= '(' 'reveal2' float ')'
color1     ::= '(' 'color1' string ')'
color2     ::= '(' 'color2' string ')'
color3     ::= '(' 'color3' string ')'
core       ::= '(' 'core' ('white' | 'black' | 'cream') ')'
margins    ::= '(' 'margin-top' float ')' '(' 'margin-bottom' float ')' '(' 'margin-left' float ')' '(' 'margin-right' float ')'
apertures  ::= '(' 'apertures' aperture* ')'
aperture   ::= '(' 'aperture' id shape width height x y radius? tool? text? font? ')'
```

### Example S-Expression Layout
```lisp
(layout
  (unit mm)
  (width 500)
  (height 400)
  (layers 2)
  (reveal1 5)
  (reveal2 5)
  (color1 "#f8fafc")
  (color2 "#f1f5f9")
  (color3 "#ffffff")
  (core white)
  (margin-top 50)
  (margin-bottom 50)
  (margin-left 50)
  (margin-right 50)
  (apertures
    (aperture (id "ap-1") (shape rectangle) (width 200) (height 150) (x 0) (y 0))
  )
)
```

---

## 3. Matboard CAD Bytecode (MCB2)

The binary bytecode standard represents a compiled `MountLayout` state:
- **Magic Header**: `MCB2` (bytes `0x4D 0x43 0x42 0x32`)
- **Key Opcodes**:
  - `0x01` Unit
  - `0x02` Width, `0x03` Height
  - `0x04` Layer count
  - `0x05` Reveal 1, `0x06` Reveal 2
  - `0x0C` Margin top, `0x0D` Margin bottom, `0x0E` Margin left, `0x0F` Margin right
  - `0x07` Color 1, `0x08` Color 2, `0x09` Color 3
  - `0x0A` Core color
  - `0x30` Apertures block (uint16 length)
- **Nested Aperture Fields**:
  - `0x01` Aperture ID (String)
  - `0x02` Aperture Shape (0=rectangle, 1=oval, 2=circle, 3=rounded, 4=text, etc.)
  - `0x03` Width, `0x04` Height, `0x05` X offset, `0x06` Y offset
  - `0x07` Corner radius (for rounded shape)
  - `0x08` Tool head
  - `0xFF` End of aperture block

---

## 4. LLM Control Rules (For AI Agents)

When generating code or parsing instructions:
1. **Preserve User Settings**: Only modify requested elements. Do not discard existing custom apertures unless explicitly told.
2. **Horizontal Distribution Formula**:
   - For $n$ apertures of width $W$ and spacing $G$ (gap):
     - Total Span $S = n \cdot W + (n - 1) \cdot G$.
     - Center offsets: $X_i = -\frac{S}{2} + \frac{W}{2} + i \cdot (W + G)$ for $i \in [0, n-1]$.
3. **Cloning / Overlapping**: When duplications are requested, offset cloned aperture coordinates by `+10mm` (or `+0.4in` depending on active unit) on both X and Y axes to prevent immediate overlapping.
4. **Licensing Modes**:
   - Passive Evaluation mode is always active.
   - Activations are validated via standard key formats (prefixes `MNT-` and `CAD-`).