anchor.diff:          abstract Life : Life with get, set
   
       /// A particle constraint.
  -    type [<StructuralEquality; NoComparison; CompilationRepresentation (CompilationRepresentationFlags.UseNullAsTrueValue)>] Constraint =
  +    type [<NoEquality; NoComparison; CompilationRepresentation (CompilationRepresentationFlags.UseNullAsTrueValue)>] Constraint =
           | Rectangle of Vector4
           | Circle of single * Vector2
           | Constraints of Constraint array
  -        | Unconstrained // OPTIMIZATION: elide Option indirection
  +        | NoConstraint // OPTIMIZATION: elide Option indirection
   
           static member (+) (constrain, constrain2) =
               match (constrain, constrain2) with
  -            | (Unconstrained, Unconstrained) -> constrain // OPTIMIZATION: elide Constraint ctor
  -            | (_, Unconstrained) -> constrain
  -            | (Unconstrained, _) -> constrain2
  +            | (NoConstraint, NoConstraint) -> constrain // OPTIMIZATION: elide Constraint ctor
  +            | (_, NoConstraint) -> constrain
  +            | (NoConstraint, _) -> constrain2
               | (_, _) -> Constraints [|constrain; constrain2|]
   
       /// The output of a particle behavior.
  
positive.code:           mutable ParticleIndex : int // operates as a ring-buffer
            mutable ParticleWatermark : int // tracks the highest active particle index; never decreases.
            Particles : 'a array // operates as a ring-buffer
            Initializer : int64 -> Constraint -> 'a Emitter -> 'a
            InPlaceBehavior : int64 -> Constraint -> 'a Emitter -> Output
            CompositionalBehaviors : CompositionalBehaviors
            ToParticlesDescriptor : int64 -> 'a Emitter -> ParticlesDescriptor
            Constraint : Constraint
            Body : Body
            Image : Image AssetTag
            Rate : single
  
negative.code:               ParticleIndex = 0
                ParticleWatermark = 0
                Particles = Array.zeroCreate particleMax
                Constraint = constrain
                Initializer = initializer
                InPlaceBehavior = inPlaceBehavior
                CompositionalBehaviors = behaviors
                ToParticlesDescriptor = toParticlesDescriptor
                Body = { Position = v2Zero; LinearVelocity = v2Zero; Rotation = 0.0f; AngularVelocity = 0.0f; Gravity = v2 0.0f -9.81f }
                Image = image
                Rate = rate
  