egnawake/screen-space-shadows ? reverse-engineered prompt

Build me a small C# OpenGL demo that shows screen space shadows on a 3D scene. I want it to load a model and a textured ground, use a movable first person camera, and render normal shadow maps plus extra contact shadows that sharpen the areas where objects touch or get very close to each other.

The scene should have a simple lit setup with a mech or similar model, a skybox or background, and a way to toggle the screen space shadow effect so I can compare before and after. Keep the controls easy, WASD to move, Q and E to go up and down, and Shift to move faster. Please make the effect work by reading from the depth buffer and marching a ray in screen or view space, so the shadows feel like the README describes.

If you need to, look up current OpenTK or AssimpNet docs online before wiring things together.