diff --git a/src/DepotDelivery.jl b/src/DepotDelivery.jl
index e02b82d..287e5b4 100644
--- a/src/DepotDelivery.jl
+++ b/src/DepotDelivery.jl
@@ -2,14 +2,15 @@ module DepotDelivery
 
 using Dates, GZip, Pkg, Scratch, Tar
 
+export BuildSpec, build, clear!
 
 #-----------------------------------------------------------------------------# __init__
 RELEASES::String = ""   # default directory to place releases: /RELEASES/$(proj.uuid)/$platform/$predicate.tar
 DEPOTS::String = ""      # default directory to reuse as a depot
 
 function __init__()
-    release_dir = @get_scratch!("RELEASES")
-    depot_dir = @get_scratch!("DEPOTS")
+    global RELEASES = @get_scratch!("RELEASES")
+    global DEPOTS = @get_scratch!("DEPOTS")
 end
 
 #-----------------------------------------------------------------------------# utils
@@ -17,12 +18,12 @@ clear!() = clear_scratch!(DepotDelivery)
 
 default_drop_patterns = (".git", ".gitignore")
 
-default_predicate(path) = !any(path -> occursin(path, default_drop_patterns), path)
+default_predicate(path) = !any(x -> occursin(x, path), default_drop_patterns)
 
 #-----------------------------------------------------------------------------# BuildSpec
 Base.@kwdef struct BuildSpec
     project_file::String = Base.current_project()
-    platforms::Vector{Base.BinaryPlatforms.Platform} = [Base.BinaryPlatforms.HostPlatform()]
+    platforms::Dict{String, Base.BinaryPlatforms.AbstractPlatform} = Dict("host" => Base.BinaryPlatforms.HostPlatform())
     tar_predicates::Dict{String, Function} = Dict("default" => default_predicate)
 end
 function Base.show(io::IO, b::BuildSpec)
@@ -43,20 +44,25 @@ function build(b::BuildSpec)
 
     # Load Project.toml
     proj = Pkg.Types.read_project(b.project_file)
+    depot = joinpath(DEPOTS, string(proj.uuid))
+    releases = joinpath(RELEASES, string(proj.uuid))
 
-    out = Dict{String, String}()
+    out = Dict{String, Dict{String, String}}(name => Dict{String, String}() for name in keys(b.platforms))
     try
-        for platform in b.platforms
-            push!(empty!(DEPOT_PATH), DEPOT)
+        for (platform_name, platform) in pairs(b.platforms)
+            push!(empty!(DEPOT_PATH), depot)
             Pkg.instantiate(; platform)
-            for (predicate_name, predicate) in b.predicates
+            for (predicate_name, predicate) in b.tar_predicates
                 @info "Creating tarball for platform `$platform` with predicate `$predicate_name`"
-                path = joinpath(RELEASES, proj.uuid, platform, predicate_name * ".tar")
-                Tar.create(predicate, DEPOT, path; portable=true)
-                out["$(proj.uuid) | $platform | $predicate_name"] = path
+                path = joinpath(releases, platform_name, predicate_name * ".tar")
+                mkpath(dirname(path))
+                Tar.create(predicate, depot, path; portable=true)
+                out[platform_name][predicate_name] = path
             end
         end
-    catch
+    catch ex
+        @warn "An error occured while building tarballs."
+        rethrow(ex)
     finally
         isnothing(_precomp_auto) || (ENV["JULIA_PKG_PRECOMPILE_AUTO"] = _precomp_auto)
         append!(empty!(DEPOT_PATH), _depot_path)