diff --git a/tidepool/default.nix b/tidepool/default.nix
index 9cac5ca..39c00f6 100644
--- a/tidepool/default.nix
+++ b/tidepool/default.nix
@@ -28,7 +28,8 @@ let
     };
   };
 
-  new = module:
+  new =
+    module:
     let
       set = lib.modules.run {
         modules = [
@@ -37,14 +38,16 @@ let
           ./src/mirrors
 
           recursiveLibModule
-        ] ++ lib.lists.from.any module;
+        ]
+        ++ lib.lists.from.any module;
       };
     in
-      set.config // {
-        inherit new;
-        inherit (set) extend;
-      };
+    set.config
+    // {
+      inherit new;
+      inherit (set) extend;
+    };
 in
-  new [
-    ./src/packages
-  ]
+new [
+  ./src/packages
+]
diff --git a/tidepool/npins/sources.json b/tidepool/npins/sources.json
index f75850d..f01a1df 100644
--- a/tidepool/npins/sources.json
+++ b/tidepool/npins/sources.json
@@ -20,9 +20,9 @@
       },
       "branch": "main",
       "submodules": false,
-      "revision": "c55943c5e8197cbc2d0e506693fd5e7e3ea0a0c3",
+      "revision": "2af4e9f1d5dfe835c0eba15be1035bfa4065aca7",
       "url": null,
-      "hash": "sha256-XBhIQ0XR1QabTgyo2c5wMk6xk/Bd3bCUlnTzRPcVfcw="
+      "hash": "sha256-fwycuhXJGDHniLlxA8Xx4IELUObrP0EW3EnsDwNdyoQ="
     }
   },
   "version": 6
diff --git a/tidepool/src/builders/basic.nix b/tidepool/src/builders/basic.nix
index 5744e2e..c365512 100644
--- a/tidepool/src/builders/basic.nix
+++ b/tidepool/src/builders/basic.nix
@@ -33,9 +33,10 @@ in
               hooks.target.target
             ];
           in
-          builtins.foldl' (
-            final: defaults: lib.dag.apply.defaults final (resolvePhases defaults)
-          ) (resolvePhases package.phases) all;
+          builtins.foldl'
+            (final: defaults: lib.dag.apply.defaults final (resolvePhases defaults))
+            (resolvePhases package.phases)
+            all;
 
         phases = lib.dag.apply.defaults phasesWithHooks {
           unpack = lib.dag.entry.before [ "patch" ] "";
@@ -91,14 +92,11 @@ in
                     foundation.stage2-coreutils
                   ]
                   ++ lib.lists.when (system == "x86_64-linux") [
-                    (lib.packages.build packages.foundation.bash.versions."5.2.15-stage1" "i686-linux" system system)
-                    .package
-                    (lib.packages.build packages.foundation.coreutils.versions."9.4-stage1" "i686-linux" system system)
-                    .package
+                    (lib.packages.build packages.foundation.bash.versions."5.2.15-stage1" "i686-linux" system system).package
+                    (lib.packages.build packages.foundation.coreutils.versions."9.4-stage1" "i686-linux" system system).package
                   ]
                   ++ lib.lists.when (system != "i686-linux" && system != "x86_64-linux") [
-                    (lib.packages.build packages.foundation.bash.versions."5.2.15-stage1" "x86_64-linux" system system)
-                    .package
+                    (lib.packages.build packages.foundation.bash.versions."5.2.15-stage1" "x86_64-linux" system system).package
                     (lib.packages.build packages.foundation.coreutils.versions."9.4-stage1" "x86_64-linux" system
                       system
                     ).package
diff --git a/tidepool/src/builders/passthrough.nix b/tidepool/src/builders/passthrough.nix
index e94381a..6a86969 100644
--- a/tidepool/src/builders/passthrough.nix
+++ b/tidepool/src/builders/passthrough.nix
@@ -6,22 +6,24 @@ let
   inherit (config.internal.packages) foundation;
 in
 {
-  config.builders.passthrough = { config }: {
-    options = {
-      settings.derivation = lib.options.create {
-        description = "The derivation to use for the package.";
-        type = lib.types.derivation;
+  config.builders.passthrough =
+    { config }:
+    {
+      options = {
+        settings.derivation = lib.options.create {
+          description = "The derivation to use for the package.";
+          type = lib.types.derivation;
+        };
+      };
+
+      config = {
+        build =
+          package:
+          package.builder.settings.derivation
+          // {
+            inherit package;
+            inherit (package) meta extend extras;
+          };
       };
     };
-
-    config = {
-      build =
-        package:
-        package.builder.settings.derivation
-        // {
-          inherit package;
-          inherit (package) meta extend extras;
-        };
-    };
-  };
 }
diff --git a/tidepool/src/lib/default.nix b/tidepool/src/lib/default.nix
index dd90003..bf0af85 100644
--- a/tidepool/src/lib/default.nix
+++ b/tidepool/src/lib/default.nix
@@ -2,8 +2,8 @@
   includes = [
     ./options.nix
     ./packages.nix
+    ./platforms.nix
     ./systems.nix
     ./types.nix
-    ./fp.nix
   ];
 }
diff --git a/tidepool/src/lib/fp.nix b/tidepool/src/lib/fp.nix
deleted file mode 100644
index 182383e..0000000
--- a/tidepool/src/lib/fp.nix
+++ /dev/null
@@ -1,14 +0,0 @@
-{ lib, config }:
-{
-  config = {
-    lib.fp = {
-      foldl =
-        f: default: items:
-        let
-          process =
-            index: if index < 0 then default else f (process (index - 1)) (builtins.elemAt items index);
-        in
-        process (builtins.length items - 1);
-    };
-  };
-}
diff --git a/tidepool/src/lib/packages.nix b/tidepool/src/lib/packages.nix
index bbb8c6f..6114e6a 100644
--- a/tidepool/src/lib/packages.nix
+++ b/tidepool/src/lib/packages.nix
@@ -92,7 +92,9 @@ in
                     global = global.config;
                   };
 
-                  prefix = package.__module__.args.dynamic.meta.prefix ++ [ "<context ${builtins.concatStringsSep path}>" ];
+                  prefix = package.__module__.args.dynamic.meta.prefix ++ [
+                    "<context ${builtins.concatStringsSep path}>"
+                  ];
                   modules = (builtins.map (context: { config = context; }) contexts) ++ [
                     {
                       freeform = lib.types.any;
diff --git a/tidepool/src/lib/platforms.nix b/tidepool/src/lib/platforms.nix
new file mode 100644
index 0000000..047796d
--- /dev/null
+++ b/tidepool/src/lib/platforms.nix
@@ -0,0 +1,92 @@
+{ config }:
+let
+  inherit (config) lib;
+in
+{
+  config.lib.platforms = {
+    from = {
+      # Converts a platform spec into a list of platforms.
+      #
+      # Example specs:
+      #
+      # {
+      #   build = "x86_64-linux";
+      #   host = "x86_64-linux";
+      #   target = "x86_64-linux";
+      # }
+      #
+      # {
+      #   build = "*";
+      #   host = "*";
+      #   target = "@host";
+      # }
+      #
+      # {
+      #   build = "*";
+      #   host = ["x86_64-linux", "aarch64-linux"];
+      #   target = "@host";
+      # }
+      #
+      # [
+      #   {
+      #     build = "*";
+      #     host = ["x86_64-linux", "aarch64-linux"];
+      #     target = "@host";
+      #   }
+      #   {
+      #     build = "i686-linux";
+      #     host = "@build";
+      #     target = "@host";
+      #   }
+      # ]
+      #
+      spec =
+        input:
+        let
+          specs = lib.lists.from.any input;
+
+          platforms = lib.lists.flatten (
+            builtins.map (
+              spec:
+              let
+                build = lib.platforms.expand spec spec.build;
+                host = lib.platforms.expand spec spec.host;
+                target = lib.platforms.expand spec spec.target;
+              in
+              builtins.concatMap (
+                build:
+                builtins.concatMap (
+                  host:
+                  builtins.map (target: {
+                    build = build;
+                    host = if host == "@build" then build else host;
+                    target =
+                      if target == "@host" then
+                        host
+                      else if target == "@build" then
+                        build
+                      else
+                        target;
+                  }) target
+                ) host
+              ) build
+            ) specs
+          );
+        in
+        platforms;
+    };
+
+    expand =
+      spec: value:
+      if builtins.isList value then
+        builtins.concatMap (system: lib.platforms.expand spec system) value
+      else if value == "@build" then
+        lib.platforms.expand spec spec.build
+      else if value == "@build" || value == "@host" then
+        [ value ]
+      else if lib.strings.hasPrefix "@" value then
+        lib.systems.doubles.${lib.strings.removePrefix "@" value}
+      else
+        [ value ];
+  };
+}
diff --git a/tidepool/src/lib/systems.nix b/tidepool/src/lib/systems.nix
index f89d39c..e7869a0 100644
--- a/tidepool/src/lib/systems.nix
+++ b/tidepool/src/lib/systems.nix
@@ -25,7 +25,8 @@ let
       lib.attrs.match patterns;
 
   getDoubles =
-    predicate: builtins.map lib.systems.into.double (builtins.filter predicate lib.systems.doubles.all);
+    predicate:
+    builtins.map lib.systems.into.double (builtins.filter predicate lib.systems.doubles.resolved);
 in
 {
   config = {
@@ -2788,11 +2789,7 @@ in
           // (builtins.removeAttrs settings [ "system" ]);
 
           assertions = builtins.foldl' (
-            result:
-              { assertion, message }:
-                if assertion resolved then
-                  result
-                else builtins.throw message
+            result: { assertion, message }: if assertion resolved then result else builtins.throw message
           ) true (resolved.system.abi.assertions or [ ]);
         in
         assert resolved.useAndroidPrebuilt -> resolved.isAndroid;
diff --git a/tidepool/src/lib/types.nix b/tidepool/src/lib/types.nix
index d0c48e5..051a934 100644
--- a/tidepool/src/lib/types.nix
+++ b/tidepool/src/lib/types.nix
@@ -172,84 +172,91 @@ in
               result.config;
           };
 
-          submodule = { config, meta, name ? "builder" }: {
-            options = {
-              __modules__ = lib.options.create {
-                description = "User specified modules for the builder definition.";
-                type = lib.types.list.of (initial // { merge = lib.options.merge.one; });
-                internal = true;
-                default.value = [ ];
-              };
-
-              extend = lib.options.create {
-                description = "Extend the package definition.";
-                type = lib.types.function lib.types.raw;
-                default.value =
-                  module:
-                  let
-                    normalized =
-                      if builtins.isList module then
-                        module
-                      else if builtins.isFunction module || module ? config then
-                        [ module ]
-                      else
-                        [
-                          {
-                            config = module;
-                          }
-                        ];
-
-                    modules = config.__modules__ ++ normalized;
-
-                    result = lib.modules.run {
-                      prefix = meta.prefix;
-
-                      args = {
-                        global = global.config;
-                      };
-
-                      modules = [
-                        submodule
-                        { config.__modules__ = modules; }
-                      ]
-                      ++ modules;
-                    };
-                  in
-                  result.config;
-              };
-
-              name = lib.options.create {
-                description = "The name of the builder.";
-                type = lib.types.string;
-                default = lib.attrs.when (name != "builder") {
-                  value = name;
+          submodule =
+            {
+              config,
+              meta,
+              name ? "builder",
+            }:
+            {
+              options = {
+                __modules__ = lib.options.create {
+                  description = "User specified modules for the builder definition.";
+                  type = lib.types.list.of (initial // { merge = lib.options.merge.one; });
+                  internal = true;
+                  default.value = [ ];
                 };
-                writable = false;
-              };
 
-              build = lib.options.create {
-                description = "The build function which takes a package definition and creates a derivation.";
-                type = lib.types.function lib.types.artifact;
-              };
+                extend = lib.options.create {
+                  description = "Extend the package definition.";
+                  type = lib.types.function lib.types.raw;
+                  default.value =
+                    module:
+                    let
+                      normalized =
+                        if builtins.isList module then
+                          module
+                        else if builtins.isFunction module || module ? config then
+                          [ module ]
+                        else
+                          [
+                            {
+                              config = module;
+                            }
+                          ];
 
-              settings = lib.options.create {
-                description = "The settings for the builder.";
-                type = lib.types.submodule ({ config }: {});
-                default.value = { };
+                      modules = config.__modules__ ++ normalized;
+
+                      result = lib.modules.run {
+                        prefix = meta.prefix;
+
+                        args = {
+                          global = global.config;
+                        };
+
+                        modules = [
+                          submodule
+                          { config.__modules__ = modules; }
+                        ]
+                        ++ modules;
+                      };
+                    in
+                    result.config;
+                };
+
+                name = lib.options.create {
+                  description = "The name of the builder.";
+                  type = lib.types.string;
+                  default = lib.attrs.when (name != "builder") {
+                    value = name;
+                  };
+                  writable = false;
+                };
+
+                build = lib.options.create {
+                  description = "The build function which takes a package definition and creates a derivation.";
+                  type = lib.types.function lib.types.artifact;
+                };
+
+                settings = lib.options.create {
+                  description = "The settings for the builder.";
+                  type = lib.types.submodule ({ config }: { });
+                  default.value = { };
+                };
               };
             };
-          };
 
           type = (lib.types.coerceWithLocation initial transform final) // {
             name = "Builder";
             description = "a builder";
           };
         in
-          type // {
-            children = type.children // {
-              inherit submodule;
-            };
+        type
+        // {
+          children = type.children // {
+            inherit submodule;
           };
+        };
 
       aliases =
         let
@@ -331,6 +338,28 @@ in
             };
           };
         };
+
+        spec = lib.types.submodule (
+          { config }:
+          {
+            options = {
+              build = lib.options.create {
+                description = "The build platform for the package.";
+                type = lib.types.string;
+              };
+
+              host = lib.options.create {
+                description = "The host platform for the package.";
+                type = lib.types.string;
+              };
+
+              target = lib.options.create {
+                description = "The target platform for the package.";
+                type = lib.types.string;
+              };
+            };
+          }
+        );
       };
 
       artifact =
@@ -696,30 +725,9 @@ in
 
                 platforms = lib.options.create {
                   description = "The platforms that the package supports.";
-                  type = lib.types.list.of (
-                    lib.types.submodule (
-                      { config }:
-                      {
-                        options = {
-                          build = lib.options.create {
-                            description = "The build platform for the package.";
-                            type = lib.types.string;
-                          };
-
-                          host = lib.options.create {
-                            description = "The host platform for the package.";
-                            type = lib.types.string;
-                          };
-
-                          target = lib.options.create {
-                            description = "The target platform for the package.";
-                            type = lib.types.string;
-                          };
-                        };
-                      }
-                    )
-                  );
+                  type = lib.types.either lib.types.platforms.spec (lib.types.list.of lib.types.platforms.spec);
                   default.value = [ ];
+                  apply = spec: lib.platforms.from.spec spec;
                 };
 
                 platform =
@@ -859,7 +867,7 @@ in
                         ]
                       );
                     in
-                      lib.types.either type (lib.types.attrs.of type);
+                    lib.types.either type (lib.types.attrs.of type);
                   default.value = null;
                 };