diff --git a/Project.toml b/Project.toml
index b3f5fab..b7bd2f3 100644
--- a/Project.toml
+++ b/Project.toml
@@ -4,11 +4,14 @@ name = "AngleBetweenVectors"
 author = "Jeffrey Sarnoff <jeffrey.sarnoff@gmail.com>"
 uuid = "ec570357-d46e-52ed-9726-18773498274d"
 repo = "https://github.com/JeffreySarnoff/AngleBetweenVectors.jl.git"
-version = "v0.3.0"
+version = "v0.4.0"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 
+[compat]
+julia = "1"
+
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
diff --git a/src/AngleBetweenVectors.jl b/src/AngleBetweenVectors.jl
index 2415a20..f036d60 100644
--- a/src/AngleBetweenVectors.jl
+++ b/src/AngleBetweenVectors.jl
@@ -4,6 +4,7 @@ import Base: angle
 
 import LinearAlgebra: norm
 
+Floats = Union{AbstractFloat, Complex{T} where T<:AbstractFloat}
 
 @inline unitize(p) = p ./ norm(p)
 
@@ -20,11 +21,20 @@ Prefer this to `acos` alternatives
 Suggested when any |coordinate| of either point may be outside 2^±20 or [1/1_000_000, 1_000_000].
 Strongly recommended when any |coordinate| is outside 2^±24 or [1/16_000_000, 16_000_000].
 
-If one of the points is at the origin, the result is zero.
+If either of the points is at the origin, the result is `NaN` because angle is undefined in that case.
 
 You *must* define a tuple constructor `Tuple(x::YourPointType) = ...` if one does not already exist.
 """
-function angle(point1::A, point2::A) where {N,T<:Real,NT<:NTuple{N,T}, V<:Vector{T}, A<:Union{NT,V}}
+angle(tuple1::NTuple{N,T}, tuple2::NTuple{N,T}) where {N, T<:Floats} = angle(real(T), tuple1, tuple2)
+
+# because of the broadcasts .- and .+ below, it is essential to check size compatibility
+# for arrays, whereas for tuples the consistency ensured by the "N" in the type
+function angle(a1::AbstractArray{T}, a2::AbstractArray{T}) where {T<:Floats}
+	size(a1) == size(a2) || throw(DimensionMismatch())
+    return angle(real(T), a1, a2)
+end
+
+function angle(::Type{T}, point1, point2) where {T<:AbstractFloat}
     unitpoint1 = unitize(point1)
     unitpoint2 = unitize(point2)
 
@@ -36,6 +46,12 @@ function angle(point1::A, point2::A) where {N,T<:Real,NT<:NTuple{N,T}, V<:Vector
     !(signbit(a) || signbit(T(pi) - a)) ? a : (signbit(a) ? zero(T) : T(pi))
 end
 
+# this method allows the arrays to have different types, even non-float types
+function angle(a1::AbstractArray{T1}, a2::AbstractArray{T2}) where {T1 <: Number, T2 <: Number}
+    T = float(promote_type(T1, T2)) # the "T" for T(pi) must be a float type
+    return angle(convert(AbstractArray{T}, a1), convert(AbstractArray{T}, a2))
+end
+
 @inline angle(point1::T, point2::T) where {T} = angle(Tuple(point1), Tuple(point2))
 
 end # AngleBetweenVectors
diff --git a/test/runtests.jl b/test/runtests.jl
index 07b811e..884ef89 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -18,3 +18,10 @@ point2 = (0.0,  1.0, 0.0, -1.0)
 # note: 2pi/3 !== Float64(2*BigFloat(pi)/3)
 @test angle(point1, point2) == Float64(2*BigFloat(pi)/3)
 @test angle(point1, point2) == angle(point2, point1)
+
+@test (@inferred angle(0:1, -1:0)) == pi/2 # abstract vector
+@test (@inferred angle(0:1, -1.0:0.0)) == pi/2 # different eltype
+@test (@inferred angle(Real[0.0 1], Int16[-1 0])) == pi/2 # array
+@test (@inferred angle(0:1, (-1.0:0.0)*1im)) == pi/2 # complex
+
+@test isnan(@inferred angle(zeros(2), 1:2)) # zero point returns NaN