diff --git a/src/charts.jl b/src/charts.jl
index b74ead2..beb761d 100644
--- a/src/charts.jl
+++ b/src/charts.jl
@@ -217,7 +217,7 @@ function _normals(tangents::SVector{2,SVector{2,T}}, ::Type{Val{0}}) where {T}
 
     t = tangents[1]
     s = tangents[2]
-    v = (t[1]*s[2] - t[2]*s[1])/2
+    v = abs(t[1]*s[2] - t[2]*s[1])/2
     # n[3] = tangents[1] × tangents[2]
     # l = norm(n)
 
diff --git a/src/overlap.jl b/src/overlap.jl
index bef6432..ef94ed3 100644
--- a/src/overlap.jl
+++ b/src/overlap.jl
@@ -106,3 +106,35 @@ function overlap(p::Simplex{3,3,0,4,T}, q::Simplex{3,3,0,4,T}) where T
     all(0+tol .<= u .<= 1-tol) && return true
     return false
 end
+
+
+
+function overlap(p::Simplex{2,2,0,3,T}, q::Simplex{2,2,0,3,T}) where T
+
+    #   tol = sqrt(eps(T))
+    tol = 1e3 * eps(T)
+
+  # Are the patches in the same plane?
+  u1 = q.tangents[1]
+  u2 = q.tangents[2]
+  v = p.vertices[1] - q.vertices[2]
+
+  for i in 1:3
+    a = p.vertices[mod1(i+1,3)]
+    b = p.vertices[mod1(i+2,3)]
+    c = p.vertices[i]
+    t = b - a
+    m = StaticArrays.SVector{2,T}(t[2],-t[1])
+
+    sp = zeros(T,3); sp[i] = dot(c-a, m)
+    sq = T[dot(q.vertices[j]-a, m) for j in 1:3]
+
+    minp, maxp = extrema(sp)
+    minq, maxq = extrema(sq)
+
+    maxq <= minp + tol && return false
+    maxp <= minq + tol && return false
+  end
+
+  return true
+end
diff --git a/src/plotlyjs_glue.jl b/src/plotlyjs_glue.jl
index 9fc87d2..d57f0e3 100644
--- a/src/plotlyjs_glue.jl
+++ b/src/plotlyjs_glue.jl
@@ -44,6 +44,44 @@ function __init__()
             return s
         end
 
+        @eval function patch(Γ::CompScienceMeshes.AbstractMesh{2}, fcr=nothing;
+            caxis=nothing, showscale=true, color="red", kwargs...)
+        
+            v = vertexarray(Γ)
+            c = cellarray(Γ)
+        
+            x = v[:,1];    y = v[:,2];    z = zeros(length(y))
+            i = c[:,1].-1; j = c[:,2].-1; k = c[:,3].-1
+        
+        
+            if fcr != nothing
+                m, M = extrema(fcr)
+                if caxis != nothing
+                    m, M = caxis
+                end
+        
+                s = PlotlyBase.mesh3d(;
+                    x=x, y=y, z=z,
+                    i=i, j=j, k=k,    
+                    intensitymode="cell",
+                    intensity=fcr,
+                    colorscale="Viridis",
+                    showscale=showscale,
+                    cmin=m,
+                    cmax=M,
+                    kwargs...
+                )
+            else
+                s = PlotlyBase.mesh3d(;
+                    x=x, y=y, z=z,
+                    i=i, j=j, k=k,
+                    color=color,
+                    kwargs...
+                )
+            end
+            return s
+        end
+
         @eval function patch(a::Vector{<:Simplex}; kwargs...)
             vertices = reduce(vcat, [v.vertices for v in a])
             faces = collect(SVector(3*(i-1)+1, 3*(i-1)+2, 3*(i-1)+3) for i in 1:length(a))
diff --git a/test/test_overlap.jl b/test/test_overlap.jl
index 437fca0..b1c34d2 100644
--- a/test/test_overlap.jl
+++ b/test/test_overlap.jl
@@ -2,59 +2,92 @@ using Test
 using CompScienceMeshes
 using StaticArrays
 
-p = simplex(
-    point(0,0,0),
-    point(1,0,0),
-    point(0,1,0))
-
-q1 = simplex(
-    point(0.6, 0.6, 0.0),
-    point(1.6, 0.6, 0.0),
-    point(0.6, 1.6, 0.0),
-)
-
-q2 = simplex(
-    point(0.4, 0.4, 0.0),
-    point(1.4, 0.4, 0.0),
-    point(0.4, 1.4, 0.0),
-)
-
-@test overlap(p, q1) == false
-@test overlap(p, q2) == true
-
-q1 = simplex(
-    point(0.949726718617726,-0.278864925637586,0.142314838273285),
-    point(0.989821441880933,0.0,-0.142314838273285),
-    point(0.989821441880933,0.0,0.142314838273285),
-)
-
-q2 = simplex(
-    point(0.949726718617726,-0.278864925637586,-0.142314838273285),
-    point(0.989821441880933,0.0,-0.142314838273285),
-    point(0.949726718617726,-0.278864925637586,0.142314838273285),
-)
-
-@test overlap(q1, q2) == false
-
-## make sure the submesh function work for 1D meshes
-
-
-l1 = meshsegment(1.0,1/2)
-vt = skeleton(l1,0)
-bd = boundary(l1)
-
-overlaps = overlap_gpredicate(bd)
-# pred1 = c -> overlaps(simplex(vertices(vt,c)))
-pred1 = c -> overlaps(chart(vt,c))
-@test pred1(CompScienceMeshes.SimplexGraph(1))
-@test !pred1(CompScienceMeshes.SimplexGraph(2))
-@test pred1(CompScienceMeshes.SimplexGraph(3))
-
-
-# test a case where the segments are:
-#   not of unit length
-#   colinear and opposite
-#   meet in a common point
-ch1 = simplex(point(1/3,0,0), point(1/3,1/3,0))
-ch2 = simplex(point(1/3,1/3,0), point(1/3,2/3,0))
-@test !overlap(ch1, ch2)
+let # udim 3
+    p = simplex(
+        point(0,0,0),
+        point(1,0,0),
+        point(0,1,0))
+
+    q1 = simplex(
+        point(0.6, 0.6, 0.0),
+        point(1.6, 0.6, 0.0),
+        point(0.6, 1.6, 0.0),
+    )
+
+    q2 = simplex(
+        point(0.4, 0.4, 0.0),
+        point(1.4, 0.4, 0.0),
+        point(0.4, 1.4, 0.0),
+    )
+
+    @test overlap(p, q1) == false
+    @test overlap(p, q2) == true
+
+    q1 = simplex(
+        point(0.949726718617726,-0.278864925637586,0.142314838273285),
+        point(0.989821441880933,0.0,-0.142314838273285),
+        point(0.989821441880933,0.0,0.142314838273285),
+    )
+
+    q2 = simplex(
+        point(0.949726718617726,-0.278864925637586,-0.142314838273285),
+        point(0.989821441880933,0.0,-0.142314838273285),
+        point(0.949726718617726,-0.278864925637586,0.142314838273285),
+    )
+
+    @test overlap(q1, q2) == false
+
+    ## make sure the submesh function work for 1D meshes
+
+
+    l1 = meshsegment(1.0,1/2)
+    vt = skeleton(l1,0)
+    bd = boundary(l1)
+
+    overlaps = overlap_gpredicate(bd)
+    # pred1 = c -> overlaps(simplex(vertices(vt,c)))
+    pred1 = c -> overlaps(chart(vt,c))
+    @test pred1(CompScienceMeshes.SimplexGraph(1))
+    @test !pred1(CompScienceMeshes.SimplexGraph(2))
+    @test pred1(CompScienceMeshes.SimplexGraph(3))
+
+
+    # test a case where the segments are:
+    #   not of unit length
+    #   colinear and opposite
+    #   meet in a common point
+    ch1 = simplex(point(1/3,0,0), point(1/3,1/3,0))
+    ch2 = simplex(point(1/3,1/3,0), point(1/3,2/3,0))
+    @test !overlap(ch1, ch2)
+end
+
+let # udim 2
+    p = simplex(
+        point(0,0),
+        point(1,0),
+        point(0,1))
+
+    q1 = simplex(
+        point(0.6, 0.6),
+        point(1.6, 0.6),
+        point(0.6, 1.6),
+    )
+
+    q2 = simplex(
+        point(0.4, 0.4),
+        point(1.4, 0.4),
+        point(0.4, 1.4),
+    )
+
+    @test overlap(p, q1) == false
+    @test overlap(p, q2) == true
+
+
+    # test a case where the segments are:
+    #   not of unit length
+    #   colinear and opposite
+    #   meet in a common point
+    ch1 = simplex(point(1/3,0), point(1/3,1/3))
+    ch2 = simplex(point(1/3,1/3), point(1/3,2/3))
+    @test !overlap(ch1, ch2)
+end
\ No newline at end of file
diff --git a/test/test_patches.jl b/test/test_patches.jl
index 403c156..1dbbebc 100644
--- a/test/test_patches.jl
+++ b/test/test_patches.jl
@@ -1,6 +1,7 @@
 using Test
 using CompScienceMeshes
 
+# universe dimension 3
 for T in [Float32, Float64]
     local mesh = meshrectangle(T(1.0), T(1.0), T(1.0))
     # local faces = skeleton(mesh, 2)
@@ -19,3 +20,23 @@ for T in [Float32, Float64]
         point(T, 0.0, 0.0, -1.0)]
     @test p.volume == T(0.5)
 end
+
+
+# universe dimension 2
+for T in [Float32, Float64]
+    local mesh = meshrectangle(T(1.0), T(1.0), T(1.0),2)
+    # local faces = skeleton(mesh, 2)
+    # local verts = cellvertices(mesh, 1)
+    p = chart(mesh, cells(mesh)[1])
+    #p = simplex(verts)
+
+    @test p.vertices == [
+        point(T, 0.0, 0.0),
+        point(T, 0.0, 1.0),
+        point(T, 1.0, 0.0)]
+    @test p.tangents == [
+        point(T, -1.0, 0.0),
+        point(T, -1.0, 1.0)]
+    @test p.normals == []
+    @test p.volume == T(0.5)
+end