# Style: field instrument A way for a part to look and be made: a small precise instrument that is also a little bit of a toy. Use it when the user asks for this style by name, or for something "like a synth / a lab instrument / a toy that is a tool". It changes proportions, edges and layout — never the fit, the fasteners or the checks. The numbers below were measured off shipped hand-held instruments in this manner, from scale drawings and renders. They are a starting point to keep, not a range to wander in. ## The idea in five rules 1. **One simple solid.** A thin slab, a box or a cylinder. Not a sculpted shell, not a stack of shapes. 2. **One module, and everything on it.** Pick a pitch and put every hole, key, knob, pocket and edge margin on it or on half of it. 3. **Flat faces, detail only where something touches.** Large uninterrupted planes; features only where a finger, a screw, a cable or a foot goes. 4. **One gesture.** Exactly one control or feature is larger, rounder or odder than the rest: a big dial, a dish, a crank, a handle that is also the stand. 5. **The process shows.** A machined part looks machined, a moulded part looks moulded. Do not mix the two looks in one body. ## Proportions | kind of part | plan ratio | thickness | |---|---|---| | hand-held, desk object | about √2 : 1 (1.36–1.45) | 6–10 % of the short side; more only for a stated reason | | long control strip | about 2.75 : 1 | 5–10 mm | | character object, speaker | 1 : 1 | as the contents need | ## Edges | body | plan corners (vertical edges) | top perimeter | bottom perimeter | |---|---|---|---| | machined metal look | radius ≈ 5 % of the short side (3 mm at 62, 5 mm at 102) | crisp, or a 0.3–0.5 mm break | a larger chamfer, 1–1.5 mm, so the part reads as floating on its feet | | moulded plastic look | 0–0.5 mm: near-sharp | crisp | crisp | Keep every radius constant along its edge. No blends between features, no domes. ## Layout - **Module**: often a multiple of 2.5 mm (7.5, 12.5), or 8 mm when the part should take LEGO-compatible pins. Keys sit on 12.5–24 mm pitches; secondary controls sit on twice the key pitch. - **Margins**: one small margin, repeated — about 4.5 mm on a hand-held, or one module. Every row of features shares an edge line with another row. - **Gaps between keys**: 0.3–1 mm. - **Pockets and caps**: a cap stands 0.5 mm inside its pocket on every side (15 mm cap in a 16 mm pocket), its corners rounded 1.5–1.75 mm, pocket corners near-sharp. - **Knobs**: a small cap in a larger recessed ring — Ø8 in Ø16, Ø6.4 caps on narrow strips. One knob may be the gesture. ## Holes and grilles - **Grille**: holes on a square grid, hole diameter 0.55–0.75 of the pitch (Ø1.15 on 2.0, Ø1.6 on 2.2, Ø3.0 on 4.0), in one rectangular or round field on a flat face. One field per face. - **For a print**, keep the web between grille holes at 1.2 mm or more (three lines of a 0.4 mm nozzle): Ø2.8 on a 4 mm pitch, not Ø3.0. - **Fasteners** hidden on the top face; countersunk or recessed underneath. Standard metric only: `holeFor`, `clearance`, `counterbore`, `countersink`. - **Feet**: four round recesses for bumpers, one module in from the corners and never over a screw. ## Colour and marks - A neutral body and at most **one accent** on the single most important feature. Colour means something: red or orange is record, stop or danger. - A part is one colour when printed, so express the accent as geometry: the caps as their own body (`return { body, caps }`), a ring, a deeper pocket. - Labels, when there are any, are lowercase, small and on the module. There is no text operation yet; do not fake letters from boxes. ## Do not - Round the top perimeter of a moulded body, or leave a metal body's plan corners sharp. - Scatter features off the module "to balance" a layout. - Add a second gesture, a second accent, or a decorative feature with no job. - Copy a real product's face, name or model code. Use the style's rules, not anyone's product. ## Before you call it done The style makes small features, and small features make thin walls and collisions that every number in `evaluate_part` passes. Two checks, every time: 1. `measure_wall_thickness` with `threshold_mm` set to the process minimum (1.2 for a 0.4 mm nozzle). Read every `thin_spots` entry; a spot between two features you did not mean to touch is a defect, not a style choice. 2. For a part in several bodies, `between_bodies`: caps `touching` their pocket floors, nothing `interfering`. Then tell the user the thinnest wall and where it is, in the same reply as the part. A pocket that leaves 1 mm under it, a grille hole that nicks a screw boss and a cable channel that leaves a 0.01 mm sliver under a slot have all shipped from this style once, and all three were visible to check 1. `examples/field-instrument/` has two parts built by these rules: `control-box.js` (moulded) and `desk-stand.js` (machined).