At first i drew a sketch on A4 paper. 

Then i created the tonal draft in Photoshop. 

I added details in the room. 

When i began added patterns on hills, i understood, that it visually mixed with boy's silhouette.  

Therefore i made cells and strips lighter 

But now the picture is not enough contrast and i fixed it.

The next step is coloring. 

And in the final i changed some details in coloring.