diff --git a/AGENTS.md b/AGENTS.md
index 4d3f471..34872ed 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -2,7 +2,7 @@
 
 ## Project Overview
 
-`cuber` is a simple cube timer application.
+`cuber` is an OpenGL 3D renderer with multiple scenes.
 
 ## Build System
 
@@ -15,7 +15,7 @@
   ```sh
   cmake -S . -B build -GNinja
   ninja -C build
-  .\build\cuber.exe
+  ./build/cuber
   ```
 
 ### Dependencies
@@ -36,7 +36,8 @@ The project is split into static libraries:
 
 - **`cbt_opengl`** — OpenGL abstraction and window management (window, context, buffer, texture, vao, shader, descriptor)
 - **`cbt_scene`** — Base scene class
-- **`scenes_cube`** — Cube scene implementation
+- **`scenes_cube`** — Spinning cube scene implementation
+- **`scenes_sphere`** — Cube-to-sphere mapped mesh with diffuse lighting
 
 ### CMake Module Path
 
@@ -120,6 +121,8 @@ cuber/
   scenes/             # Application scenes
     cube.hpp          # Spinning cube scene
     cube.cpp          # Cube scene implementation
+    sphere.hpp        # Cube-to-sphere mapped mesh
+    sphere.cpp        # Sphere scene implementation
   deps/               # Custom Find*.cmake scripts
     Findfmt.cmake     # fmt library
 ```
diff --git a/README.md b/README.md
index d98e5f7..0a70b12 100644
--- a/README.md
+++ b/README.md
@@ -1,30 +1,49 @@
-# cuber
-
-`cuber` is a simple cube timer.
-
-## Requirements
-
-- CMake 3.21+
-- Ninja
-- C++23 compiler
-
-## Development
-
-**Configure**:
-
-```sh
-cmake -S . -B build -GNinja
-```
-
-**Build**:
-
-```sh
-ninja -C build
-```
-
-**Run**:
-
-```bash
-./build/cuber.exe
-```
-
+# cuber
+
+`cuber` is an OpenGL 3D renderer with multiple scenes.
+
+## Requirements
+
+- CMake 3.21+
+- Ninja
+- C++23 compiler
+
+All dependencies (fmt, GLFW, GLAD, asio, GLM, stb) are fetched
+automatically via CMake FetchContent.
+
+## Development
+
+**Configure**:
+
+```sh
+cmake -S . -B build -GNinja
+```
+
+**Build**:
+
+```sh
+ninja -C build
+```
+
+**Run**:
+
+```sh
+./build/cuber
+```
+
+## Usage
+
+```
+--duration <seconds>  Auto-terminate after N seconds (for testing/CI)
+--scene <cube|sphere> Select initial scene (default: cube)
+--screenshot          Render one frame, save screenshot, and exit
+S key                 Take screenshot (saved as screenshot.png)
+1/2 key               Switch between cube/sphere scene
+Q key                 Quit
+```
+
+## Scenes
+
+- **cube** — spinning colored cube with per-face colors
+- **sphere** — cube-to-sphere mapped mesh with per-face colors and
+  diffuse lighting