schema_version: 1
name: chiral-keyplate
intent: 'Model the square key plate described in the attached text spec as one solid. Frame: origin
  at the plate centre in XY, z = 0 on the bottom face, +z through the thickness, +x and +y along
  the plate edges. Cut four identical rectangular slots from the top as 4 mm-deep pockets in a C4
  pinwheel whose first slot is centred at (20, 8) mm with its long axis along x; the other three
  are 90 degree rotations about z. The pinwheel is chiral — do not emit the mirrored arrangement,
  a centred cross, or any pattern with a mirror plane. Name the four pocket floors. One solid; export
  STEP and STL.'
units:
  length: mm
  angle: deg
material: null
density_kg_m3: null
process: null
release_status: reconstruction
frame:
  origin: 'The intersection of the plate''s two XY centre lines, projected onto the bottom face:
    [0, 0, 0]. This is the centre of the bottom square, not the three-dimensional centre of the
    solid. Source: chiral-keyplate-spec.md:3-5.'
  axes:
    x: Along plateWidth and the long side of slot A, from the x = -40 edge toward x = +40. Slot
      A has positive x = 20. In the top view looking from +z toward the bottom, draw +x to the right.
    y: Along plateHeight, perpendicular to +x, from the y = -40 edge toward y = +40. Slot A has
      positive y = 8. In the same top view draw +y upward, establishing the signed source coordinates.
    z: 'Normal to the bottom, pointing through the material toward the top: bottom z = 0, top z
      = plateThickness = 8. The frame is right-handed; positive rotations about +z are counter-clockwise
      viewed from +z.'
  datums:
  - name: bottomDatum
    description: The intact bottom plane z = 0, outward normal -z. It fixes the thickness origin;
      all four nominal floors are 4 mm above it.
  - name: xCentreDatum
    description: The vertical midplane x = 0, halfway between the x = -40 and x = +40 edges; positive
      x is the side containing slot A's centre.
  - name: yCentreDatum
    description: The vertical midplane y = 0, halfway between the y = -40 and y = +40 edges; positive
      y is the side containing slot A's centre.
  - name: topDatum
    description: The remaining top face z = plateThickness = 8, outward normal +z. Pocket depth
      is measured downward from this plane; each floor is at plateThickness - slotDepth = 4.
envelope:
  min:
  - -40
  - -40
  - 0
  max:
  - 40
  - 40
  - 8
  tolerance: 0.05
parameters:
- name: plateWidth
  value: 80
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:22, "plateWidth (80 mm)"
  tolerance: 0.01
  description: Overall x span, centred about x = 0; independent of plateHeight.
- name: plateHeight
  value: 80
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:22, "plateHeight (80 mm)"
  tolerance: 0.01
  description: Overall y span, centred about y = 0; equal to plateWidth at nominal values only.
- name: plateThickness
  value: 8
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:22, "plateThickness (8 mm)"
  tolerance: 0.01
  description: Bottom-to-top z span. The bottom remains at zero during edits; pockets follow the
    top while retaining slotDepth.
  edit_test:
    delta: 2
    expect:
      volume_delta: 12800
      direction: increase
      tolerance_rel: 0.002
      bbox_delta:
      - 0
      - 0
      - 2
- name: slotLength
  value: 16
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:23, "slotLength (16 mm)"
  tolerance: 0.01
  description: Long dimension of each rectangular pocket; along x for A/C and y for B/D.
  edit_test:
    delta: 2
    expect:
      volume_delta: -192
      direction: decrease
      tolerance_rel: 0.002
      bbox_delta:
      - 0
      - 0
      - 0
- name: slotWidth
  value: 6
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:23, "slotWidth (6 mm)"
  tolerance: 0.01
  description: Short dimension perpendicular to each slot's long axis.
- name: slotDepth
  value: 4
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:23, "slotDepth (4 mm)"
  tolerance: 0.01
  description: Pocket depth downward from the top; all floors follow plateThickness - slotDepth.
    Lines 7-8 require blind pockets.
- name: slotCentreX
  value: 20
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:23, "slotCentreX (20 mm)"
  tolerance: 0.01
  description: Signed x coordinate of slot A; use positive quarter-turn rotations to place B/C/D.
- name: slotCentreY
  value: 8
  unit: mm
  provenance: stated
  source: sources/chiral-keyplate-spec.md:24, "slotCentreY (8 mm, the centre of slot A)"
  tolerance: 0.01
  description: Signed y coordinate of slot A; preserve its positive sign and the specified chirality.
features:
- id: plateBlank
  kind: extrude
  count: 1
  description: 'A square rectangular prism, nominally 80 by 80 by 8 mm, centred in XY with bottom
    z = 0. Subtract the four blind pockets to leave one solid. The continuous web below their floors
    has thickness plateThickness - slotDepth. Source: chiral-keyplate-spec.md:3-8.'
  parameters:
  - plateWidth
  - plateHeight
  - plateThickness
  - slotDepth
  verify:
  - method: bbox
  - method: solid
    points:
    - - 0
      - 0
      - 2
    - - 0
      - 0
      - 6
    - - -36
      - -36
      - 4
    - - 36
      - 36
      - 4
    note: Interior points check the intact centre and outer plate material.
  - method: section
    section: lowerWeb
  - method: count
    section: lowerWeb
    count: 1
    note: One outer solid loop beneath the pockets; holes are separately required to be zero.
- id: slotA
  kind: pocket
  count: 1
  description: 'Slot A is the 16 by 6 mm rectangle at centre (slotCentreX, slotCentreY) = (20, 8),
    long axis x, obtained from A by a positive 0 deg rotation about +z. Nominal bounds x = [12,
    28], y = [5, 11]; cut from top z = 8 to floor z = 4. Name its floor pocketFloorA. Source: chiral-keyplate-spec.md:7-15,25-26.'
  parameters:
  - plateThickness
  - slotLength
  - slotWidth
  - slotDepth
  - slotCentreX
  - slotCentreY
  verify:
  - method: void
    points:
    - - 20
      - 8
      - 6
    - - 13
      - 8
      - 6
    - - 27
      - 8
      - 6
    - - 20
      - 6
      - 6
    - - 20
      - 10
      - 6
    note: Centre and four interior probes span both rectangle dimensions; positive 0 deg rotations
      of the slot A probes. Minimum wall clearance is 1 mm.
  - method: solid
    points:
    - - 20
      - 8
      - 2
    - - 11
      - 8
      - 6
    - - 29
      - 8
      - 6
    - - 20
      - 4
      - 6
    - - 20
      - 12
      - 6
    note: Material below the floor and 1 mm outside each plan wall establishes a blind, bounded
      pocket. Positive 0 deg rotations of the slot A material probes.
  - method: section
    section: slotALongitudinal
  - method: section
    section: slotATransverse
  - method: face
    face: pocketFloorA
- id: slotB
  kind: pocket
  count: 1
  description: 'Slot B is the 16 by 6 mm rectangle at centre (-slotCentreY, slotCentreX) = (-8,
    20), long axis y, obtained from A by a positive 90 deg rotation about +z. Nominal bounds x =
    [-11, -5], y = [12, 28]; cut from top z = 8 to floor z = 4. Name its floor pocketFloorB. Source:
    chiral-keyplate-spec.md:7-15,25-26.'
  parameters:
  - plateThickness
  - slotLength
  - slotWidth
  - slotDepth
  - slotCentreX
  - slotCentreY
  verify:
  - method: void
    points:
    - - -8
      - 20
      - 6
    - - -8
      - 13
      - 6
    - - -8
      - 27
      - 6
    - - -6
      - 20
      - 6
    - - -10
      - 20
      - 6
    note: Centre and four interior probes span both rectangle dimensions; positive 90 deg rotations
      of the slot A probes. Minimum wall clearance is 1 mm.
  - method: solid
    points:
    - - -8
      - 20
      - 2
    - - -8
      - 11
      - 6
    - - -8
      - 29
      - 6
    - - -4
      - 20
      - 6
    - - -12
      - 20
      - 6
    note: Material below the floor and 1 mm outside each plan wall establishes a blind, bounded
      pocket. Positive 90 deg rotations of the slot A material probes.
  - method: section
    section: pocketBand
  - method: face
    face: pocketFloorB
- id: slotC
  kind: pocket
  count: 1
  description: 'Slot C is the 16 by 6 mm rectangle at centre (-slotCentreX, -slotCentreY) = (-20,
    -8), long axis x, obtained from A by a positive 180 deg rotation about +z. Nominal bounds x
    = [-28, -12], y = [-11, -5]; cut from top z = 8 to floor z = 4. Name its floor pocketFloorC.
    Source: chiral-keyplate-spec.md:7-15,25-26.'
  parameters:
  - plateThickness
  - slotLength
  - slotWidth
  - slotDepth
  - slotCentreX
  - slotCentreY
  verify:
  - method: void
    points:
    - - -20
      - -8
      - 6
    - - -13
      - -8
      - 6
    - - -27
      - -8
      - 6
    - - -20
      - -6
      - 6
    - - -20
      - -10
      - 6
    note: Centre and four interior probes span both rectangle dimensions; positive 180 deg rotations
      of the slot A probes. Minimum wall clearance is 1 mm.
  - method: solid
    points:
    - - -20
      - -8
      - 2
    - - -11
      - -8
      - 6
    - - -29
      - -8
      - 6
    - - -20
      - -4
      - 6
    - - -20
      - -12
      - 6
    note: Material below the floor and 1 mm outside each plan wall establishes a blind, bounded
      pocket. Positive 180 deg rotations of the slot A material probes.
  - method: section
    section: pocketBand
  - method: face
    face: pocketFloorC
- id: slotD
  kind: pocket
  count: 1
  description: 'Slot D is the 16 by 6 mm rectangle at centre (slotCentreY, -slotCentreX) = (8, -20),
    long axis y, obtained from A by a positive 270 deg rotation about +z. Nominal bounds x = [5,
    11], y = [-28, -12]; cut from top z = 8 to floor z = 4. Name its floor pocketFloorD. Source:
    chiral-keyplate-spec.md:7-15,25-26.'
  parameters:
  - plateThickness
  - slotLength
  - slotWidth
  - slotDepth
  - slotCentreX
  - slotCentreY
  verify:
  - method: void
    points:
    - - 8
      - -20
      - 6
    - - 8
      - -13
      - 6
    - - 8
      - -27
      - 6
    - - 6
      - -20
      - 6
    - - 10
      - -20
      - 6
    note: Centre and four interior probes span both rectangle dimensions; positive 270 deg rotations
      of the slot A probes. Minimum wall clearance is 1 mm.
  - method: solid
    points:
    - - 8
      - -20
      - 2
    - - 8
      - -11
      - 6
    - - 8
      - -29
      - 6
    - - 4
      - -20
      - 6
    - - 12
      - -20
      - 6
    note: Material below the floor and 1 mm outside each plan wall establishes a blind, bounded
      pocket. Positive 270 deg rotations of the slot A material probes.
  - method: section
    section: pocketBand
  - method: face
    face: pocketFloorD
- id: chiralPinwheel
  kind: pattern
  count: 4
  description: 'Exactly the four pockets A/B/C/D above, including seed A, related by R(x, y) = (-y,
    x) at 0, 90, 180 and 270 deg about +z. This feature describes their relationship, not four additional
    cuts. Preserve the specified handedness; no mirrored arrangement, centred cross or pattern with
    a mirror plane is acceptable. Source: chiral-keyplate-spec.md:7-20.'
  parameters:
  - plateThickness
  - slotLength
  - slotWidth
  - slotDepth
  - slotCentreX
  - slotCentreY
  verify:
  - method: section
    section: pocketBand
    note: Exactly four inner holes in one connected outer solid loop.
  - method: count
    section: pocketBand
    count: 1
    note: This probe counts outer solid loops, not pockets; SectionExpect.holes is the four-pocket
      count.
  - method: solid
    points:
    - - -20
      - 8
      - 6
    - - 8
      - 20
      - 6
    - - 20
      - -8
      - 6
    - - -8
      - -20
      - 6
    note: Centres of the forbidden x-reflected pockets must remain material. Together with actual
      slot-centre void probes and named floor centroids, these discriminate handedness in the fixed
      frame.
  - method: solid
    points:
    - - 20
      - 0
      - 6
    - - 0
      - 20
      - 6
    - - -20
      - 0
      - 6
    - - 0
      - -20
      - 6
    note: Axis-arm points remain material; these also reject a centred cross.
  - method: face
    face: pocketFloorA
  - method: face
    face: pocketFloorB
  - method: face
    face: pocketFloorC
  - method: face
    face: pocketFloorD
interfaces: []
acceptance:
  bbox_tolerance: 0.05
  volume:
    expected: 49664
    tolerance_rel: 0.002
    provenance: derived
    note: plateWidth * plateHeight * plateThickness - 4 * slotLength * slotWidth * slotDepth = 51200
      - 1536 = 49664 mm^3. The four pockets do not intersect or reach the outer edges.
  surface_area:
    expected: 16064
    tolerance_rel: 0.002
    provenance: derived
    note: 2 * (plateWidth * plateHeight + plateWidth * plateThickness + plateHeight * plateThickness)
      + 4 * 2 * (slotLength + slotWidth) * slotDepth = 15360 + 704 = 16064 mm^2. Removed top areas
      equal the four added floor areas; only pocket sidewall area is a net addition.
  center_of_mass:
    expected:
    - 0
    - 0
    - 3.9381443298969074
    tolerance: 0.05
    provenance: derived
    note: Uniform-density geometric centroid. Let V0 = plateWidth * plateHeight * plateThickness,
      Vr = 4 * slotLength * slotWidth * slotDepth and V = V0 - Vr. The four slot centres sum to
      (0, 0), giving x = y = 0. z = (V0 * plateThickness / 2 - Vr * (plateThickness - slotDepth
      / 2)) / V = 195584 / 49664 = 382 / 97 mm. Material density is not needed for this geometric
      centroid.
  solid_count: 1
  sections:
  - id: lowerWeb
    plane: z
    at: 2
    expect:
      area: 6400
      area_tolerance_rel: 0.002
      loops: 1
      holes: 0
    description: At z = (plateThickness - slotDepth) / 2 = 2, below every floor. Area = plateWidth
      * plateHeight = 6400 mm^2; one unperforated square region.
  - id: pocketBand
    plane: z
    at: 6
    expect:
      area: 6016
      area_tolerance_rel: 0.002
      loops: 1
      holes: 4
    description: At z = plateThickness - slotDepth / 2 = 6, through all four cavities. Solid area
      = plateWidth * plateHeight - 4 * slotLength * slotWidth = 6016 mm^2. One outer material loop
      and four separate rectangular inner holes.
  - id: slotALongitudinal
    plane: y
    at: 8
    expect:
      area: 576
      area_tolerance_rel: 0.002
      loops: 1
      holes: 0
    description: The xz section at y = slotCentreY = 8 intersects only slot A along its long axis.
      Area = plateWidth * plateThickness - slotLength * slotDepth = 576 mm^2. Its top-open notch
      is part of the outer loop, not an inner hole.
  - id: slotATransverse
    plane: x
    at: 20
    expect:
      area: 616
      area_tolerance_rel: 0.002
      loops: 1
      holes: 0
    description: The yz section at x = slotCentreX = 20 intersects only slot A across its short
      axis. Area = plateHeight * plateThickness - slotWidth * slotDepth = 616 mm^2. Its top-open
      notch is part of the outer loop, not an inner hole.
  faces:
  - name: pocketFloorA
    plane: z
    at: 4
    normal: +
    area: 96
    area_tolerance_rel: 0.002
    tolerance: 0.05
    center:
    - 20
    - 8
    mode: one
  - name: pocketFloorB
    plane: z
    at: 4
    normal: +
    area: 96
    area_tolerance_rel: 0.002
    tolerance: 0.05
    center:
    - -8
    - 20
    mode: one
  - name: pocketFloorC
    plane: z
    at: 4
    normal: +
    area: 96
    area_tolerance_rel: 0.002
    tolerance: 0.05
    center:
    - -20
    - -8
    mode: one
  - name: pocketFloorD
    plane: z
    at: 4
    normal: +
    area: 96
    area_tolerance_rel: 0.002
    tolerance: 0.05
    center:
    - 8
    - -20
    mode: one
  deviation: null
  blockout:
    volume_min: 51097.6
    volume_max: 51302.4
  export_volume_tolerance_rel: 0.002
references:
- path: sources/chiral-keyplate-spec.md
  kind: text
  role: authoritative
  sha256: 0036c51f5df296508a684f749dc85a5e789cc0b325273221082d1a28eff95798
  units: mm
  revision: Unversioned supplied text; SHA-256 identifies the source revision.
  note: Complete dimensional and handedness specification, including the eight required parameter
    names and four separately identifiable pocket floors. Supplied short hash 0036c51f5df2 matches.
    There are no images, drawings, reference meshes or reference-ingest outputs.
open_questions:
- What material and density, if any, should be assigned for physical mass reporting? Neither is
  specified; both remain null and no mass is claimed.
- What manufacturing process and physical production tolerances, if any, apply? They are not specified;
  process remains null and digital comparison tolerances are not manufacturing tolerances.