use abstract "amber/Platform"

and each load / build must somehow map it to
either amber_core/Platform-Browser or amber_core/Platform-Node

index.html

@@ -20,6 +20,7 @@
             clearInterval(__interval);
             require.baseUrl = base;
             require.paths['helios/app'] = require.paths['helios/index'].replace("index", "app");
+            require.map["*"]["amber/Platform"] = "amber_core/Platform-Browser";
             require.callback = function () {
               require(["helios/app"], function (amber) {
                 amber.initialize({'transport.defaultAmdNamespace': "amber_core"});