diff --git a/libmach/README.md b/libmach/README.md
index a30f077c..3344952c 100644
--- a/libmach/README.md
+++ b/libmach/README.md
@@ -4,8 +4,9 @@ Build the `libmach` dynamic library by running `make` (or running `zig build` in
 The resulting binary should be located in `libmach/build/`.
 
 Test the functionality of `libmach` using `make test_c` and `make test_lisp`.
-These commands use C and Lisp to call into `libmach`, and both should show a blank window for exactly 1 second.
+These commands use C and Lisp to call into `libmach`, and both should show a blank window for 5 seconds.
+If you resize the window, it should print the new dimensions to the standard output.
 
-Note: `make test_lisp` requires a relatively recent version of Steel Bank Common Lisp (`sbcl`) to be installed.
+Note: `make test_lisp` requires a relatively recent version of Steel Bank Common Lisp (`sbcl`) to be installed, plus Quicklisp.
 
-You can find the Zig source code for `libmach` in `src/bindings.zig`.
+You can find the Zig source code for `libmach` in `src/platform/libmach.zig`.
diff --git a/libmach/test.c b/libmach/test.c
index 4583a45b..07b1e67b 100644
--- a/libmach/test.c
+++ b/libmach/test.c
@@ -1,40 +1,46 @@
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdbool.h>
 
-typedef void mach_core_callback(void*);
+typedef void resize_callback(void*, uint32_t, uint32_t);
 
 // `libmach` exported API bindings
-void mach_core_set_init(mach_core_callback);
-void mach_core_set_update(mach_core_callback);
-void mach_core_set_deinit(mach_core_callback);
-void mach_run(void);
-void core_set_should_close(void*);
-float core_delta_time(void*);
+void* mach_init_core(void);
+void mach_deinit(void*);
+void mach_set_should_close(void*);
+bool mach_window_should_close(void*);
+int mach_update(void*, resize_callback);
+float mach_delta_time(void*);
+
+void resize_fn(void* core, uint32_t width, uint32_t height) {
+  printf("Resize callback: %u %u\n", width, height);
+}
 
 static float elapsed = 0;
 
-void my_init(void* core) {
-  printf("My init!\n");
-}
-
-void my_update(void* core) {
-  float dt = core_delta_time(core);
-  if (elapsed < 1.0) {
-    elapsed += dt;
-  } else {
-    core_set_should_close(core);
-  }
-  printf("My update! total time = %f\n", elapsed);
-}
-
-void my_deinit(void* core) {
-  printf("My deinit!\n");
-}
-
 int main() {
-  mach_core_set_init(my_init);
-  mach_core_set_update(my_update);
-  mach_core_set_deinit(my_deinit);
-  mach_run();
+  void* core = mach_init_core();
+
+  if (core == 0) {
+    printf("Error instantiating mach core\n");
+    return 0;
+  }
+
+  while (!mach_window_should_close(core)) {
+    if (mach_update(core, resize_fn) == 0) {
+      printf("Error updating Mach\n");
+      break;
+    };
+
+    elapsed += mach_delta_time(core);
+    if (elapsed > 5.0) {
+      mach_set_should_close(core);
+    }
+
+    // printf("Elapsed: %f\n", elapsed);
+  }
+
+  mach_deinit(core);
+
   return 0;
 }
diff --git a/libmach/test.lisp b/libmach/test.lisp
index 9423b4ba..d51c5ac4 100644
--- a/libmach/test.lisp
+++ b/libmach/test.lisp
@@ -15,50 +15,51 @@
 
 ;; Note: CFFI automatically translates C_style names into lispier kebab-case ones
 
-;; typedef void mach_core_callback(void*);
-(defctype mach-core-callback :pointer)
+;; void* mach_init(void);
+(defcfun "mach_init_core" :pointer)
+;; for some reason, calling "mach_init" always returns a null pointer, and I have no clue why...
+;; So I renamed the API function name to "mach_init_core" instead
 
-;; void mach_core_set_init(mach_core_callback);
-(defcfun "mach_core_set_init" :void
-  (callback mach-core-callback))
+;; int mach_update(void*, resize_callback);
+(defcfun "mach_update" :int
+  (core :pointer) (resize-fn :pointer))
 
-;; void mach_core_set_update(mach_core_callback);
-(defcfun "mach_core_set_update" :void
-  (callback mach-core-callback))
+;; void mach_deinit(void*);
+(defcfun "mach_deinit" :void
+  (core :pointer))
 
-;; void mach_core_set_deinit(mach_core_callback);
-(defcfun "mach_core_set_deinit" :void
-  (callback mach-core-callback))
+;; void mach_set_should_close(void*);
+(defcfun "mach_set_should_close" :void
+  (core :pointer))
 
-;; void mach_run(void);
-(defcfun "mach_run" :void)
+;; float mach_delta_time(void*);
+(defcfun "mach_delta_time" :float
+  (core :pointer))
 
-;; void core_set_should_close(void*);
-(defcfun "core_set_should_close" :void (core :pointer))
-
-;; float core_delta_time(void*);
-(defcfun "core_delta_time" :float (core :pointer))
-
-(defcallback my-init :void ((core :pointer))
-  (format t "Hello from my-init!~%"))
+;; bool mach_window_should_close(void*);
+(defcfun "mach_window_should_close" :bool
+  (core :pointer))
 
+;; main
 (defvar *elapsed* 0.0)
 
-(defcallback my-update :void ((core :pointer))
-  (format t "Hello from my-update ~a~%" *elapsed*)
-  (if (< *elapsed* 1.0)
-      (incf *elapsed* (core-delta-time core))
-      (core-set-should-close core)))
+(defcallback resize-fn :void ((core :pointer) (width :unsigned-int) (height :unsigned-int))
+  (format t "Resize Callback: ~S ~S~%" width height))
 
-(defcallback my-deinit :void ((core :pointer))
-  (format t "Hello from my-deinit!~%"))
+(setf core (mach-init-core))
 
-(mach-core-set-init (callback my-init))
+(format t "Core: ~S~%" core)
 
-(mach-core-set-update (callback my-update))
+(when (pointer-eq core (null-pointer))
+  (format t "Failed to initialize mach core~%")
+  (sb-ext:exit))
 
-(mach-core-set-deinit (callback my-deinit))
-
-(mach-run)
+(loop while (not (mach-window-should-close core))
+      do (progn
+           (when (= 0 (mach-update core (callback resize-fn)))
+             (format t "Error updating mach~%")
+             (sb-ext:exit))
+           (when (> (incf *elapsed* (mach-delta-time core)) 5.0)
+             (mach-set-should-close core))))
 
 (sb-ext:exit)
diff --git a/src/bindings.zig b/src/bindings.zig
deleted file mode 100644
index 71f5e78c..00000000
--- a/src/bindings.zig
+++ /dev/null
@@ -1,52 +0,0 @@
-const std = @import("std");
-const gpu = @import("gpu");
-const Core = @import("Core.zig");
-const libmach = @import("platform/libmach.zig");
-const native = @import("platform/native.zig");
-
-// Current Limitations:
-// 1. Currently, ecs seems to be using some weird compile-time type trickery, so I'm not exactly sure how
-// `engine` should be integrated into the C API
-// 2. Core might need to expose more state so more API functions can be exposed (for example, the WebGPU API)
-// 3. Be very careful about arguments, types, memory, etc - any mismatch will result in undefined behavior
-
-pub const App = libmach;
-
-pub export fn mach_core_set_init(core_init: libmach.CoreCallback) void {
-    std.debug.print("mach core set init\n", .{});
-    libmach.core_callbacks.core_init = core_init;
-}
-
-pub export fn mach_core_set_deinit(core_deinit: libmach.CoreCallback) void {
-    std.debug.print("mach core set deinit\n", .{});
-    libmach.core_callbacks.core_deinit = core_deinit;
-}
-
-pub export fn mach_core_set_update(core_update: libmach.CoreCallback) void {
-    std.debug.print("mach core set update\n", .{});
-    libmach.core_callbacks.core_update = core_update;
-}
-
-pub export fn mach_run() void {
-    if (libmach.core_callbacks.core_init == null) {
-        std.debug.print("Did not provide a core_init callback\n", .{});
-        return;
-    }
-    if (libmach.core_callbacks.core_update == null) {
-        std.debug.print("Did not provide a core_update callback\n", .{});
-        return;
-    }
-    if (libmach.core_callbacks.core_deinit == null) {
-        std.debug.print("Did not provide a core_deinit callback\n", .{});
-        return;
-    }
-    native.main() catch unreachable;
-}
-
-pub export fn core_set_should_close(core: *Core) void {
-    core.*.setShouldClose(true);
-}
-
-pub export fn core_delta_time(core: *Core) f32 {
-    return core.*.delta_time;
-}
diff --git a/src/platform/libmach.zig b/src/platform/libmach.zig
index d521cf07..03ed2160 100644
--- a/src/platform/libmach.zig
+++ b/src/platform/libmach.zig
@@ -2,34 +2,106 @@ const std = @import("std");
 const Core = @import("../Core.zig");
 const gpu = @import("gpu");
 const ecs = @import("ecs");
+const glfw = @import("glfw");
 
 pub const App = @This();
 
-// Zig says that *App has a size of 0 bits, and it won't compile if
-// pub const core_callback_t = fn (*App, *Core) callconv(.C) void;
-// What is *App needed for anyway?
-pub const CoreCallback = fn (*Core) callconv(.C) void;
+// Dummy init, deinit, and update functions
+pub fn init(_: *App, _: *Core) !void { }
 
-pub const CoreCallbacks = struct {
-    core_init: ?CoreCallback,
-    core_update: ?CoreCallback,
-    core_deinit: ?CoreCallback,
-};
+pub fn deinit(_: *App, _: *Core) void { }
 
-pub var core_callbacks = CoreCallbacks {
-    .core_init = null,
-    .core_update = null,
-    .core_deinit = null,
-};
+pub fn update(_: *App, _: *Core) !void { }
 
-pub fn init(_: *App, core: *Core) !void {
-    core_callbacks.core_init.?(core);
+// Current Limitations:
+// 1. Currently, ecs seems to be using some weird compile-time type trickery, so I'm not exactly sure how
+// `engine` should be integrated into the C API
+// 2. Core might need to expose more state so more API functions can be exposed (for example, the WebGPU API)
+// 3. Be very careful about arguments, types, memory, etc - any mismatch will result in undefined behavior
+
+pub export fn mach_set_should_close(core: *Core) void {
+    core.setShouldClose(true);
 }
 
-pub fn deinit(_: *App, core: *Core) void {
-    core_callbacks.core_deinit.?(core);
+pub export fn mach_delta_time(core: *Core) f32 {
+    return core.delta_time;
 }
 
-pub fn update(_: *App, core: *Core) !void {
-    core_callbacks.core_update.?(core);
+var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+const allocator = gpa.allocator();
+
+// Initializes and returns Mach's core structure
+// Uses an optional type so it is valid to return 0 (on an error)
+// TODO: come up with a better error reporting system
+pub export fn mach_init_core() ?*Core {
+    const core: *Core = allocator.create(Core) catch {
+        return @intToPtr(?*Core, 0); // on error, return null pointer
+    };
+    core.* = Core.init(allocator) catch {
+        return @intToPtr(?*Core, 0); // on error, return null pointer
+    };
+
+    // // Glfw specific: initialize the user pointer used in callbacks
+    core.*.internal.initCallback();
+
+    return core;
+}
+
+// Deinitializes mach core structure
+pub export fn mach_deinit(core: *Core) void {
+    core.internal.deinit();
+    allocator.destroy(core);
+}
+
+pub export fn mach_window_should_close(core: *Core) bool {
+    return core.internal.window.shouldClose();
+}
+
+pub const CoreCallback = fn (*Core, u32, u32) callconv(.C) void;
+
+// Adapted from native.zig
+pub export fn mach_update(core: *Core, resize_fn: ?CoreCallback) i32 {
+    if (core.internal.wait_event_timeout > 0.0) {
+        if (core.internal.wait_event_timeout == std.math.inf(f64)) {
+            // Wait for an event
+            glfw.waitEvents() catch {
+                return 0;
+            };
+        } else {
+            // Wait for an event with a timeout
+            glfw.waitEventsTimeout(core.internal.wait_event_timeout) catch {
+                return 0;
+            };
+        }
+    } else {
+        // Don't wait for events
+        glfw.pollEvents() catch {
+            return 0;
+        };
+    }
+
+    core.delta_time_ns = core.timer.lapPrecise();
+    core.delta_time = @intToFloat(f32, core.delta_time_ns) / @intToFloat(f32, std.time.ns_per_s);
+
+    var framebuffer_size = core.getFramebufferSize();
+    core.target_desc.width = framebuffer_size.width;
+    core.target_desc.height = framebuffer_size.height;
+
+    if (core.swap_chain == null or !core.current_desc.equal(&core.target_desc)) {
+        const use_legacy_api = core.surface == null;
+        if (!use_legacy_api) {
+            core.swap_chain = core.device.nativeCreateSwapChain(core.surface, &core.target_desc);
+        } else core.swap_chain.?.configure(
+            core.swap_chain_format,
+            .{ .render_attachment = true },
+            core.target_desc.width,
+            core.target_desc.height,
+        );
+
+        if (resize_fn != null) {
+            resize_fn.?(core, core.target_desc.width, core.target_desc.height);
+        }
+        core.current_desc = core.target_desc;
+    }
+    return 1;
 }
diff --git a/src/platform/native.zig b/src/platform/native.zig
index 4e7f2c07..8848946b 100644
--- a/src/platform/native.zig
+++ b/src/platform/native.zig
@@ -222,7 +222,7 @@ pub const Platform = struct {
         platform.events.append(node);
     }
 
-    fn initCallback(platform: *Platform) void {
+    pub fn initCallback(platform: *Platform) void {
         platform.user_ptr = UserPtr{ .platform = platform };
 
         platform.window.setUserPointer(&platform.user_ptr);