Sure, here's a sample HTML file with a game where you can drag a light source to illuminate a pitch black area. There is also a cube in the middle that casts a shadow and affects the light.
To play the game, you can open the HTML file in a web browser, and you will see a black area with a yellow circular light source and a gray cube in the middle. You can click and drag the light source to move it around. The cube will cast a shadow based on the position of the light source. When the light is inside the cube, the shadow disappears.