diff --git a/engine-proto/engine.jl b/engine-proto/engine.jl
deleted file mode 100644
index df75fbe..0000000
--- a/engine-proto/engine.jl
+++ /dev/null
@@ -1,105 +0,0 @@
-module Engine
-
-export Construction, mprod
-
-import Subscripts
-using LinearAlgebra
-using AbstractAlgebra
-using Groebner
-
-# --- primitve elements ---
-
-mutable struct Point{T}
-  coords::Union{Vector{MPolyRingElem{T}}, Nothing}
-  vec::Union{Vector{MPolyRingElem{T}}, Nothing}
-  
-  ## [to do] constructor argument never needed?
-  Point{T}(vec::Union{Vector{MPolyRingElem{T}}, Nothing} = nothing) where T = new(vec)
-end
-
-coordnames(_::Point) = [:xₚ, :yₚ, :zₚ]
-
-function buildvec(pt::Point, coordqueue)
-  pt.coords = splice!(coordqueue, 1:3)
-  coordring = parent(coordqueue[1])
-  pt.vec = [one(coordring), dot(pt.coords, pt.coords), pt.coords...]
-end
-
-mutable struct Sphere{T}
-  coords::Union{Vector{MPolyRingElem{T}}, Nothing}
-  vec::Union{Vector{MPolyRingElem{T}}, Nothing}
-  
-  Sphere{T}(vec::Union{Vector{MPolyRingElem{T}}, Nothing} = nothing) where T = new(vec)
-end
-
-coordnames(_::Sphere) = [:rₛ, :sₛ, :xₛ, :yₛ, :zₛ]
-
-function buildvec(sph::Sphere, coordqueue)
-  sph.coords = splice!(coordqueue, 1:5)
-  sph.vec = sph.coords
-end
-
-# --- primitive relations ---
-
-abstract type Relation{T} end
-
-mprod(v, w) = v[1]*w[2] + w[1]*v[2] - dot(v[3:end], w[3:end])
-
-struct LiesOn{T} <: Relation{T}
-  pt::Point{T}
-  sph::Sphere{T}
-end
-
-struct AlignsWithBy{T} <: Relation{T}
-  sph_v::Sphere{T}
-  sph_w::Sphere{T}
-  cos_angle::T
-end
-
-# --- constructions ---
-
-mutable struct Construction{T}
-  points::Vector{Point{T}}
-  spheres::Vector{Sphere{T}}
-  
-  Construction{T}(; points = Point{T}[], spheres = Sphere{T}[]) where T = new{T}(points, spheres)
-end
-
-function Base.push!(ctx::Construction{T}, elem::Point{T}) where T
-  push!(ctx.points, elem)
-end
-
-function Base.push!(ctx::Construction{T}, elem::Sphere{T}) where T
-  push!(ctx.spheres, elem)
-end
-
-function realize(ctx::Construction{T}) where T
-  # collect variable names
-  allcoordnames = Symbol[]
-  elements = vcat(ctx.points, ctx.spheres)
-  for (index, elem) in enumerate(elements)
-    subscript = Subscripts.sub(string(index))
-    append!(allcoordnames,
-      [Symbol(name, subscript) for name in coordnames(elem)]
-    )
-  end
-  
-  # construct coordinate ring
-  coordring, coordqueue = polynomial_ring(parent_type(T)(), allcoordnames)
-  
-  # construct coordinate vectors
-  for elem in elements
-    buildvec(elem, coordqueue)
-  end
-end
-
-end
-
-# ~~~ sandbox setup ~~~
-
-a = Engine.Point{Rational{Int64}}()
-b = Engine.Point{Rational{Int64}}()
-s = Engine.Sphere{Rational{Int64}}()
-ctx = Engine.Construction{Rational{Int64}}(points = [a])
-Engine.push!(ctx, b)
-Engine.push!(ctx, s)
\ No newline at end of file