Plotting and geometry

src/common/plotting.ts — angles, bearings, segment intersection, polyomino rotations/reflections, and matrix transforms.

Angles use table facing: 0° is due north and increases clockwise (matching board-game convention). toggleFacing converts to/from standard planar angles (0° east, counterclockwise).

Direction and angles

Export	Description
`deg2dir`	Maps compass bearings in degrees (multiples of 45) to `Direction` labels
`dir2deg`	Maps `Direction` labels to compass bearings in degrees
`rotateFacing(facing, delta)`	Rotates a facing by `delta` degrees (rounded to the nearest 45°)
`normDeg(deg)`	Normalizes a degree measurement to `[0, 360)`
`deg2rad(deg)`	Converts degrees to radians
`rad2deg(rad)`	Converts radians to degrees
`toggleFacing(n)`	Converts between table facing and planar angles
`smallestDegreeDiff(deg1, deg2)`	Signed shortest angular difference from `deg2` to `deg1`, in `(-180, 180]`

Points and bearings

Export	Description
`projectPoint(x, y, dist, deg)`	Projects from `(x, y)` by `dist` along table-facing `deg`; returns `[newX, newY]`
`calcBearing(x1, y1, x2, y2)`	Table-facing bearing from point 1 to point 2
`ptDistance(x1, y1, x2, y2)`	Euclidean distance between two points
`midpoint(x1, y1, x2, y2)`	Midpoint between two points
`circle2poly(cx, cy, r, steps?)`	Approximates a circle as a polygon (default 64 vertices)
`distFromCircle(circle, point)`	Shortest distance from a point to a circle's circumference

Segment intersection

Export	Description
`pointOnSegment(p, q, r)`	Whether `q` lies on the closed segment `pr` (bounding-box test)
`pointOrientation(p, q, r)`	Orientation of triplet `(p, q, r)`: `0` collinear, `1` clockwise, `2` counterclockwise
`linesIntersect(p1, q1, p2, q2)`	Whether segments `p1q1` and `p2q2` intersect (including collinear overlap)

Matrix transforms

Export	Description
`transposeRect(lst)`	Transposes a rectangular 2D array (all rows must have equal length)
`matrixRectRot90(lst)`	Rotates a square matrix +90° (transpose, then reverse rows)
`matrixRectRotN90(lst)`	Rotates a square matrix −90° (reverse rows, then transpose)

Polyomino symmetry

Export	Description
`Delta`	Relative offset `{ dx, dy, payload }` for labelled shape points
`allRotationsAndReflections(deltas, options?)`	All unique D4 rotations/reflections of a delta-shape; retains each point's `payload`. Options: `includeReflections` (default `true`), `normalize` (`"none"` or `"minToOrigin"`)

Example games

Ponte del Diavolo — line intersection
Minefield — polyomino transforms
Armadas — bearings and projection