Fake polygonal shadows (modelled objects with semi transparent black or grey material) are about useless on anything but flat ground. In other words, if you make some flat grassless field with rare trees, then 3d fake shadows are ok, but if you think about dropping shadow on fence, then you’ll fail with this method.

But… Shadows are able to give extra dramatic low poly look for the scene in game. So seems it’s time to try baking. Additionally one could bake occlusion and some other graphic goods.

Soon I’ll test and describe results here. In my work I’ll use this tutorial:

https://scicomp.ethz.ch/public/manual/Blender/2.79/render/blender_render/bake.html

Interesting note from another forum:

The Sun Lamp and Spot Lamp are the only two that cast real shadows in the BGE.

The new info for me. I thought that the only way to get shadows is to use spot lamp! Gotta try dat.