> But with constraint-based systems, the layout might be literally under- or over-determined, in the sense that there might be more than one, or less than one, layouts that satisfy your rules.
This is under the "what's wrong" section but it doesn't actually say what's wrong.
Obviously if over-specified, the extra constraints can't be followed which wouldn't be intuitive (and... css does this constantly, so it doesn't seem relevant). But surely the system could just do one of them and alert the developer which constraints can't be followed?
And for under-specification, it could use 0. Nobody's going to write a specification and then publish a site without looking at it once.
And actually, can't under/over specified constraints be statically checked? Doesn't SolveSpace do this?