diff --git a/cbt/opengl/context.cpp b/cbt/opengl/context.cpp
index a2047a7..29535be 100644
--- a/cbt/opengl/context.cpp
+++ b/cbt/opengl/context.cpp
@@ -34,6 +34,9 @@ context::context(window const& win) {
         return;
     }
     m_valid = true;
+
+    // Set initial viewport to match window size
+    glViewport(0, 0, win.width(), win.height());
 }
 
 context::~context() {}
@@ -42,4 +45,8 @@ auto context::valid() const -> bool {
     return m_valid;
 }
 
+auto context::set_size(int width, int height) -> void {
+    glViewport(0, 0, width, height);
+}
+
 }
diff --git a/cbt/opengl/context.hpp b/cbt/opengl/context.hpp
index dfa11c2..54cc085 100644
--- a/cbt/opengl/context.hpp
+++ b/cbt/opengl/context.hpp
@@ -10,6 +10,7 @@ public:
     ~context();
 
     auto valid() const -> bool;
+    auto set_size(int width, int height) -> void;
 
 private:
     bool m_valid = false;
diff --git a/cbt/scene.cpp b/cbt/scene.cpp
index 0ffdd5d..b85fafe 100644
--- a/cbt/scene.cpp
+++ b/cbt/scene.cpp
@@ -8,6 +8,6 @@ auto scene::init() -> bool {
 
 auto scene::update(float) -> void {}
 
-auto scene::render() -> void {}
+auto scene::render(int, int) -> void {}
 
 }
diff --git a/cbt/scene.hpp b/cbt/scene.hpp
index d0629dd..8d855f3 100644
--- a/cbt/scene.hpp
+++ b/cbt/scene.hpp
@@ -10,7 +10,7 @@ public:
 
     virtual auto init() -> bool;
     virtual auto update(float delta_time) -> void;
-    virtual auto render() -> void;
+    virtual auto render(int width, int height) -> void;
 };
 
 }
diff --git a/cbt/window.cpp b/cbt/window.cpp
index 2f7b061..9c10b47 100644
--- a/cbt/window.cpp
+++ b/cbt/window.cpp
@@ -52,6 +52,12 @@ window::window(std::string title, int width, int height) {
         return;
     }
 
+    m_width = width;
+    m_height = height;
+
+    glfwSetWindowUserPointer(m_window, this);
+    glfwSetWindowSizeCallback(m_window, resize_callback_impl);
+
 #ifdef _WIN32
     auto hwnd = glfwGetWin32Window(m_window);
     BOOL use_dark_mode = TRUE;
@@ -94,6 +100,29 @@ auto window::stop() -> void {
     }
 }
 
+auto window::width() const -> int {
+    return m_width;
+}
+
+auto window::height() const -> int {
+    return m_height;
+}
+
+auto window::on_resize(resize_callback cb) -> void {
+    m_resize_cb = cb;
+}
+
+auto window::resize_callback_impl(GLFWwindow* glfw_window, int width, int height) -> void {
+    auto* self = static_cast<window*>(glfwGetWindowUserPointer(glfw_window));
+    if (self) {
+        self->m_width = width;
+        self->m_height = height;
+        if (self->m_resize_cb) {
+            self->m_resize_cb(width, height);
+        }
+    }
+}
+
 auto window::screenshot(std::string filepath) const -> bool {
     if (!m_window || !valid()) {
         return false;
diff --git a/cbt/window.hpp b/cbt/window.hpp
index 8654165..180f2d3 100644
--- a/cbt/window.hpp
+++ b/cbt/window.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <functional>
 #include <string>
 
 #define GLFW_INCLUDE_NONE
@@ -19,13 +20,22 @@ public:
     auto raw() const -> GLFWwindow*;
     auto stop() -> void;
     auto screenshot(std::string filepath = "screenshot.png") const -> bool;
+    auto width() const -> int;
+    auto height() const -> int;
+
+    using resize_callback = std::function<void(int width, int height)>;
+    auto on_resize(resize_callback cb) -> void;
 
 private:
     GLFWwindow* m_window = nullptr;
+    int m_width = 0;
+    int m_height = 0;
+    resize_callback m_resize_cb;
     bool m_glfw_initialized = false;
 
     static auto init_glfw() -> bool;
     static auto terminate_glfw() -> void;
+    static auto resize_callback_impl(GLFWwindow* glfw_window, int width, int height) -> void;
 };
 
 }
diff --git a/cuber.cpp b/cuber.cpp
index 9700c57..64a7c00 100644
--- a/cuber.cpp
+++ b/cuber.cpp
@@ -57,6 +57,11 @@ auto main(int argc, char const* argv[]) -> int {
         return 1;
     }
 
+    // Wire up resize callback
+    win.on_resize([&ctx](int width, int height) {
+        ctx.set_size(width, height);
+    });
+
     auto cube_scn = cbt::scenes::cube();
     auto sphere_scn = cbt::scenes::sphere();
 
@@ -118,7 +123,7 @@ auto main(int argc, char const* argv[]) -> int {
         prev = now;
 
         active_scene->update(dt);
-        active_scene->render();
+        active_scene->render(win.width(), win.height());
 
         win.swap_buffers();
         win.poll_events();
diff --git a/scenes/cube.cpp b/scenes/cube.cpp
index cf20214..f466509 100644
--- a/scenes/cube.cpp
+++ b/scenes/cube.cpp
@@ -23,14 +23,14 @@ auto cube::init() -> bool {
 
 auto cube::update(float) -> void {}
 
-auto cube::render() -> void {
+auto cube::render(int width, int height) -> void {
     auto now = std::chrono::steady_clock::now();
     auto elapsed = std::chrono::duration<float>(now - m_start).count();
 
     glClearColor(0.15f, 0.15f, 0.2f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-    auto aspect = 1280.0f / 720.0f;
+    auto aspect = float(width) / float(height);
     auto proj = glm::perspective(glm::radians(45.0f), aspect, 0.1f, 100.0f);
     auto view = glm::translate(glm::mat4{1.0f}, glm::vec3{0.0f, 0.0f, -3.0f});
     auto model = glm::rotate(glm::mat4{1.0f}, elapsed, glm::vec3{1.0f, 0.5f, 0.3f});
diff --git a/scenes/cube.hpp b/scenes/cube.hpp
index 923de66..016faf4 100644
--- a/scenes/cube.hpp
+++ b/scenes/cube.hpp
@@ -16,7 +16,7 @@ public:
     cube();
     auto init() -> bool override;
     auto update(float delta_time) -> void override;
-    auto render() -> void override;
+    auto render(int width, int height) -> void override;
 
 private:
     opengl::shader m_prog;
diff --git a/scenes/sphere.cpp b/scenes/sphere.cpp
index 37d4276..f81411c 100644
--- a/scenes/sphere.cpp
+++ b/scenes/sphere.cpp
@@ -25,14 +25,14 @@ auto sphere::init() -> bool {
 
 auto sphere::update(float) -> void {}
 
-auto sphere::render() -> void {
+auto sphere::render(int width, int height) -> void {
     auto now = std::chrono::steady_clock::now();
     auto elapsed = std::chrono::duration<float>(now - m_start).count();
 
     glClearColor(0.15f, 0.15f, 0.2f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-    auto aspect = 1280.0f / 720.0f;
+    auto aspect = float(width) / float(height);
     auto proj = glm::perspective(glm::radians(45.0f), aspect, 0.1f, 100.0f);
     auto view = glm::translate(glm::mat4{1.0f}, glm::vec3{0.0f, 0.0f, -4.0f});
     auto model = glm::rotate(glm::mat4{1.0f}, elapsed, glm::vec3{1.0f, 0.3f, 0.2f});
diff --git a/scenes/sphere.hpp b/scenes/sphere.hpp
index 191c71a..448df3c 100644
--- a/scenes/sphere.hpp
+++ b/scenes/sphere.hpp
@@ -16,7 +16,7 @@ public:
     sphere();
     auto init() -> bool override;
     auto update(float delta_time) -> void override;
-    auto render() -> void override;
+    auto render(int width, int height) -> void override;
 
 private:
     opengl::shader m_prog;