Good job le-mec, one of the better versions of this exercise I've seen. Only two things strike me as odd - The light at the bottom of the blue block looks a little too bright/colorful, and the reflection of the floor on the near lit face of the orange block looks odd. Now for my qualifications - Desaturating the light on the blue block will make things muddy and ulgy, and the floor light on the orange should look odd because you are putting compliments together (the surface would be slightly more lit by reflected light, but the colors would be less saturated).
And about the dark line: Imagine light as a bunch of rubber bouncy-balls. If you throw them into a corner how many will hit close to the line where wall and floor meet, and how many will bounce away? It is harder for light to reach a corner, so corners are always darker and large flat regions are lighter (more lit).
[Always remember that if a topic seems uninteresting, then it's just because you are picturing a solution that lacks vigor.] - William b. Hand