On this page

Values and expressions

This page applies to model asset and module units. Sprite and sound properties use their own literal grammars.

Tokens and punctuation

Names are case-sensitive ASCII identifiers: [A-Za-z_][A-Za-z0-9_]*. Use underscores in authored names. Hyphenated property keywords such as parent-origin are language-defined; hyphens in expressions mean subtraction. Workspace export IDs have a separate lowercase naming rule.

Whitespace and newlines do not terminate declarations. Write ; after assignments, imports, parameter/port declarations, checks and motion keys. A component use block ends with };; ordinary declaration blocks end with }. Both // line comments and non-nested /* … */ comments are supported.

Strings use double quotes and remain on one line. The model/sprite lexer allows only escaped quote and escaped backslash (\" and \\). Colors use exactly six hexadecimal digits after #; alpha belongs to texture properties.

Numeric literals use decimal notation (4, 0.5, .5) with an optional unit. Use unary - for negatives. Scientific notation, NaN, and Infinity are not model numeric literals. Parentheses group expressions or form tuples; square brackets also form vectors. Vector values must match the expected arity.

Closed value types

These are the available design, component param and surface slot types. There is no arbitrary generic type constructor.

Type	Example	Meaning
`integer`	`16`	Exact unitless integer
`unit`	`4u`	Model distance
`texel`	`16px`, `16tx`	Texture distance; pixel placement must be integral
`degree`	`15deg`	Rotation angle
`second`	`0.5s`	Motion time
`ratio`	`0.5ratio`	Dimensionless ratio with an explicit type
`bool`	`true`	`true` or `false`
`color`	`#c94f2a`	RGB color
`vec2<unit>`	`(2u, 3u)`	Two model distances
`vec3<unit>`	`(2u, 3u, 4u)`	Position or size
`vec3<degree>`	`(0deg, 15deg, 0deg)`	Euler rotation
`vec3<ratio>`	`(1ratio, 1ratio, 1ratio)`	Scale/alignment ratios
`vec2<texel>`	`(0px, 8px)`	Atlas or face pixel position
`texel-rect`	`(0px, 0px, 4px, 4px)`	Four texel components

Write explicit units at API boundaries. Plain integer literals can acquire a field's expected numeric unit in supported typed contexts; explicit incompatible units are still rejected. This is not a general conversion between units.

Operators

Precedence below runs from tightest to loosest. Binary operators associate left to right within a row. Use parentheses to make intended grouping visible.

Operators	Rules
Member access and calls	`.x`, `.y`, `.z` on matching vectors; built-in calls only
Unary `+`, `-`	Numeric sign
`*`, `/`, `%`	Multiplication has at most one dimensional scalar operand; division accepts a plain divisor or matching units; remainder accepts integers
`+`, `-`	Matching units; matching vector shapes for vector addition/subtraction
`<`, `<=`, `>`, `>=`	Numeric values with compatible units; returns `bool`
`==`, `!=`	Equality/inequality; returns `bool`

Vector scaling uses a plain scalar. Model arithmetic is exact rational arithmetic: 1u / 2 is valid, but 1 / 2 cannot be represented as an integer. 4u / 2u produces integer 2. Multiplying 2u * 3u does not create an area type. Division/remainder by zero fails. There are no &&, ||, !, ternary expressions or implicit rounding; use separate named checks for separate conditions.

Built-in functions

Function	Arguments and result
`abs(x)`	One numeric value; preserves its unit
`min(a, …)`, `max(a, …)`	One or more numeric arguments of one unit
`clamp(x, lower, upper)`	Three numeric arguments of one unit; author an ordered interval
`vec2(a, b)`, `vec3(a, b, c)`	Numeric arguments with a supported shared vector unit
`texels(length, density)`	Nonnegative `unit` length and positive integer pixels per unit; returns integral `texel`, without rounding
`mirror_x(point, plane)`	`vec3<unit>` point and `unit` plane coordinate; reflects X. `mirror_y` and `mirror_z` reflect the other axes
`box_origin(anchor, size, alignment)`	`vec3<unit>`, positive `vec3<unit>`, and `vec3<ratio>` in `[0,1]`; returns `anchor - size * alignment` componentwise

Reflection functions compute points only. They do not duplicate geometry, change joint frames or flip texture contents.

Designs and dependencies

Fragment inside a model unit:

export design Dimensions {
  width: unit = 4u;
  height: unit = 4u;
  depth: unit = 4u;
  size: vec3<unit> = (Dimensions.width, Dimensions.height, Dimensions.depth);
  netWidth: texel = texels(Dimensions.width * 2 + Dimensions.depth * 2, 1);
  check positiveWidth = Dimensions.width > 0u;
  check fitsAtlas = Dimensions.netWidth <= 32px;
}

A field is referenced as Dimensions.width, even within its own design. An imported exported design uses alias.Dimensions.width. Vector fields allow component access such as Dimensions.size.x. Forward references are allowed; dependency cycles, duplicate names and namespace shadowing are rejected. Every check must evaluate to bool and be true for the candidate to compile.

A design is an immutable set of values and assertions. A check does not measure the rendered model or move a part into place. Pass values into component parameters to reuse geometry. See the complete precision example for a compiled design that resizes geometry and its UV net while preserving one-pixel eyes.

Ready to make something? Get agent instructions →