--- a/src/Grids/mapped_grid.jl	Mon Sep 16 09:53:29 2024 +0200
+++ b/src/Grids/mapped_grid.jl	Wed Oct 02 08:51:37 2024 +0200
@@ -72,8 +72,6 @@
 boundary_identifiers(g::MappedGrid) = boundary_identifiers(g.logical_grid)
 boundary_indices(g::MappedGrid, id::TensorGridBoundary) = boundary_indices(g.logical_grid, id)
 
-# Review: Error when calling plot(boundary_grid(g, id))
-# Currently need to collect first, i.e., plot(collect(boundary_grid(g, id)))
 function boundary_grid(g::MappedGrid, id::TensorGridBoundary)
     b_indices = boundary_indices(g.logical_grid, id)
 
@@ -98,9 +96,9 @@
 """
     mapped_grid(x, J, size::Vararg{Int})
 
-A `MappedGrid` with a default logical grid on a unit hyper box. `x` and `J`
-are functions to be evaluated on the logical grid and `size` determines the
-size of the logical grid.
+A `MappedGrid` with a default logical grid on the D-dimensional unit hyper 
+box [0,1]ᴰ. `x` and `J`are functions to be evaluated on the logical grid
+and `size` determines the size of the logical grid.
 """
 function mapped_grid(x, J, size::Vararg{Int})
     D = length(size)
@@ -133,17 +131,6 @@
     end
 end
 
-"""
-    metric_tensor_inverse(g::MappedGrid)
-
-The inverse of the metric tensor of `g` as a grid function.
-"""
-function metric_tensor_inverse(g::MappedGrid)
-    return map(jacobian(g)) do ∂x∂ξ
-        inv(∂x∂ξ'*∂x∂ξ)
-    end
-end
-
 function min_spacing(g::MappedGrid{T,1} where T)
     n, = size(g)
 
@@ -185,7 +172,7 @@
 """
 function normal(g::MappedGrid, boundary)
     b_indices = boundary_indices(g, boundary)
-    σ =_boundary_sign(component_type(g), boundary)
+    σ = _boundary_sign(component_type(g), boundary)
     return map(jacobian(g)[b_indices...]) do ∂x∂ξ
         ∂ξ∂x = inv(∂x∂ξ)
         k = grid_id(boundary)
@@ -193,6 +180,15 @@
     end
 end
 
+function normal(g::MappedGrid, boundary, i...)
+    σ = _boundary_sign(component_type(g), boundary)
+    ∂ξ∂x = inv(jacobian(g)[i...])
+
+    k = grid_id(boundary)
+    return σ*∂ξ∂x[k,:]/norm(∂ξ∂x[k,:])
+end
+
+
 function _boundary_sign(T, boundary)
     if boundary_id(boundary) == UpperBoundary()
         return one(T)